FAQ 1/2

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Rodney D. Van Meter

Jan 17, 1998, 3:00:00 AM1/17/98

Archive-name: arch-storage/part1
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Posting-Frequency: monthly

Rod Van Meter, Joe Stith, and the gang on<BR> or

Information on disk, tape, MO, RAID and SSD can be found in part 1 of
the FAQ. Part 2 covers file systems, hierarchical storage management,
backup software, robotics, benchmarking, MTBF and miscellaneous

$Header: /nfs/yelo/rdv/comp-arch-storage/faq/RCS/FAQ-1.draft,v 1.38 98/01/16 18:19:48 rdv Exp $

Many items merely identified, not described.

Last updated: 1997/9/18

Most recent changes:

THIC (Tape Head Interface Committee)
HD Forum @ Blue Planet
Storage system issues, both software and hardware

1. Editor's Note

2. Disclaimer

3. Original Editor's notes

4. Truly Frequently Asked Questions

5. Tape
5.1. Cartridge vs Cassette
5.2. Longitudinal
5.3. Serpentine
5.4. Helical Scan
5.5. Tape Media Lifetimes (Longevity) {Brief}
5.6. 9-track {brief}
5.7. 3480/3490/3490E {brief}
5.7.1. New IBM Tape (NTP) 3590
5.8. Magstar Coyote (IBM 3570) {Brief, New}
5.9. QIC {brief}
5.9.1. Travan TapeStor {brief,new}
5.10. 4mm {brief}
5.11. 8mm {brief}
5.11.1. Mammoth (EXB-8900) {Brief}
5.11.2. Sony SDV-300 {New}
5.12. DLT {full}
5.12.1. DLT7000 {Brief}
5.12.2. DLT4000
5.12.3. DLT2700 (from DEC)
5.12.4. DLT2000 (from DEC (now Quantum))
5.13. MountainGate (was Metrum) VHS {brief}
5.14. VCR VHS
5.15. 19MM (D1 and D2) {Brief}
5.16. ID-1
5.16.1. DATATAPE
5.16.2. Sony
5.17. D-2
5.18. StorageTek Helical {Brief}
5.19. Optical
5.20. D-6 {brief}
5.21. D-3 {brief}
5.22. Sony DTF {Brief}
5.22.1. GY-2120 {New}
5.23. DATATAPE DTR-48 {Brief}

6. Disk
6.1. CAV, ZCAV and CLV
6.2. Optical {Brief}
6.2.1. CD-ROM DVD (Digital Versatile Disk) (Next-Generation CD) {New} GIANT CD-ROMS {New}
6.2.2. WORM {brief} Sony {brief}
6.2.3. Erasable Magneto-Optical Physics Sony MiniDisc {Brief,New} Magneto-optical, 5.25-inch Magneto-optical ZCAV, 5.25-inch HP Corsair {Brief} Maxoptix T4-1300 Pinnacle Micro {New} Asaca HSMO {Brief} Other Multi-beam MO {None} 3.5-inch MO {Brief} Sony {Brief} Nikon 12-inch MO {Brief} Sony 12-inch MO {Brief} NEC 12-inch MO {Brief}
6.2.4. Electron-Trapping {None}
6.2.5. Dual Function {Brief} Panasonic/Toray {Brief} IBM {None}
6.3. Magnetic
6.3.1. 5.25-inch Seagate
6.3.2. 3.5-inch IBM
6.3.3. Hard Disk Manufacturers {Brief}
6.3.4. Bernouli {None}
6.3.5. Floptical {Brief}
6.3.6. PC Removables {Brief} SyQuest EZ135 {Brief} Iomega Zip {Brief} Iomega Jaz {Brief} SyQuest Removable Cartridge hard Drives Kalok removable cartridge hard drives
6.3.7. Mainframe {Brief}
6.4. Other

7. RAID {Full}
7.1. RAID Levels
7.2. RAID-6
7.3. John O'Brien and RAID-7
7.4. RAID Papers
7.5. R-Squared {Brief}
7.6. Sun {Brief}
7.7. Clariion {Brief}
7.8. BayDel {Brief, New}
7.9. the RAIDbook {Brief}
7.10. Software Striping {Brief}
7.11. RAID Vendors

8. Solid State Disk (SSD) Frequently Asked Questions (FAQ)

9. Other Devices
9.1. Holographic Storage Products {Brief,New}
9.2. TeraStor {Brief, New}

10. RAIT (Redundant Arrays of Inexpensive Tape)
10.1. DataVast (was VastNSS)

11. RAOT (Redundant Arrays of Other Things :-)

Subject: [1] Editor's Note
From: Editor's Note

I took over the maintenance of the C.A.S FAQ from its originator, Joe
Stith (, Fermi National Accelerator Laboratory, at the
time), in July '94. I have made many additions and edits of my own. It
should be available on the various FAQ servers. Apologies for the
under-construction formatting and lack of better referencing.

I will add as my expertise and time allows and will include
submissions sent to me (Rod Van Meter, and
information put into the newsgroup by others. Yes, some of the
submittals are from vendors (including me, see the disclaimer). If
you post to the newsgroup and find yourself quoted in this FAQ but
wish to be removed, please let me know.

There is more information in my (still primitive) WWW version of the
FAQ, including more commercial info. It is temporarily available at, but this
is probably not a good permanent home for it (volunteers?). I have
also started working on a Japanese translation available there (only
about 10% complete). There is also a good group of FAQs (including
this one) stored at;
prettier and easier to use but with only the info I actually post.

The size of these FAQs is getting out of hand; I'm open to suggestions
on material that doesn't really belong in a FAQ or areas where I'm
simply too verbose (I may reduce the DLT info since there is now a
separate FAQ).

SHMO: when you see this, it means "Somebody Help Me Out!" I'm actively
soliciting information on this topic.

See the copyright notice near the end.

Subject: [2] Disclaimer
From: Disclaimer

I used to work for ASACA, which makes Metrum's (now Mountain Gate)
robotics and makes a 12 MB/sec. magneto-optical disk drive, and
resells AMASS in Japan. I now work at USC's Information Sciences
Institute working on the Netstation project (essentially, network-attached
peripherals and high-speed networking). This information is included
so you can identify my bias. Obviously the things that I know the most
about are the best-represented. I attempt to be as impartial as
possible; if you have complaints about my fairness, let me know. None
of this should in any way be construed as the official opinions of
ASACA, USC/ISI or Caltech, and may not even represent MY opinions.

Subject: [3] Original Editor's notes
From: Original Editor's notes

I believe a reference would be useful and I am willing to pull
it together...

I have included the original call for votes and will go through that
list for other ideas to include.

I will also format this for sending to news.answers, misc.answers,
and comp.answers.

As I am writing this, "{None}" indicates I have not written anything
for it yet, {Full} indicates it is OK, while {Brief} indicates somewhere in
the middle.

{New} indicates some new information has been provided.
(joe stith, early '94)


This information is believed to be reasonably accurate although I do
not verify every submission. No legal liability is assumed. See full
disclaimer at end.

Subject: [4] Truly Frequently Asked Questions
From: Truly Frequently Asked Questions

Also see the miscellaneous section near the end of part 2 of the FAQ.

* How do I connect X to Y?

Try asking in the appropriate comp.periphs.x or comp.sys.y groups.

* What about the jumper settings for my Yoyodyne 4000?

Try asking in the appropriate comp.periphs.yoyodyne group. This group
attempts to keep the discussion at a higher level.

* Can somebody recommend a PC or Unix backup package? (SHMO)

The Aug. '94 issue of PC World has an article covering PC tape
drives (mostly QIC), and covers backup software to some extent as
well. Try asking this question in the PC-related newsgroups.

I've started adding a list of backup software to part 2 of this FAQ,
though it's not very complete yet.

* What about DAT/DLT/8mm/...?

Covered in the sections on tape drives & media. There is also a
DLT-specific FAQ maintained by a guy from DEC posted occassionally

* Does anybody have the phone number of...?

There's a long list currently posted to:
(inside FAQ) and in biz.zeos.general.

For the WWW-enabled, check out

* What about RAID7?

See the description under RAID arrays; NOT a popular topic around


This topic is responsible for generating the most heat in this group.
There are a few sentences about it in part 2 of the FAQ, but I'm not
qualified to write this section (and/or not willing to suffer the
public humiliation :-).

Subject: [5] Tape
From: Tape
(No compression added in calculations unless specified otherwise)

Subject: [5.1] Cartridge vs Cassette
From: Tape
Cartridge has only one reel (i.e. 3480, DLT). Cassettes have two
reels (i.e., 8mm, 4mm, 19mm, VHS) and may not need to be rewound to

Subject: [5.2] Longitudinal
From: Tape
have heads that write bit streams that are parallel to the edge of
the tape.

Subject: [5.3] Serpentine
From: Tape
are longitudinal that write the full length of the tape, then turn
around and write the length of the tape in the opposite direction with the
heads in a slightly different position. This process may repeat many times.

Subject: [5.4] Helical Scan
From: Tape
are like your VCR with a rotating head mounted at an angle writing
"swipes" at an angle not parallel to the edge of the tape. The tape is moved
only slightly between swipes. Two or so longitudinal tracks may also be used
for fast positioning purposes.

Subject: [5.5] Tape Media Lifetimes (Longevity) {Brief}
From: Tape

See and for some info on this
topic. Other contributions gladly accepted, this topic comes up
frequently in the newsgroup. (rdv, 1996/3/20)

Subject: [5.6] 9-track {brief}
From: Tape
The old 2400 foot round reel of tape written at 800, 1600, or 6250 BPI.

Subject: [5.7] 3480/3490/3490E {brief}
From: Tape

Square cartridge:
IBM 3480 - 18 track - 200 MB/cartridge, 1984
IBM 3490 - Smaller packaging, IDRC standard, 1989
reports that it is a 3480 in ID string
IBM 3490E - 36 track, double length - 800 MB/cartridge
native, 1992
IDRC data compression is also available.

These drives have traditionally come from the mainframe vendors --
IBM, Fujitsu, Storage Tek, etc. They were originally very large
objects, with vacuum columns and mainframe interfaces, the size of
large filing cabinets.

However, recently they have become available in smaller packages, 19"
rack mount or table top, and with interfaces such as SCSI.

Here's one from last year that I recently dug out of some old mail:

IBM has just made generally available the following:
3490E Model E SCSI tape drive
fast/wide differential
IDRC compression
3 MB/sec at the tape head, 6.5 MB/sec with compression
approx 800 MB tape capacity with out compression, 2.4 GB with a 3:1 comp
7 tape CSL(cartridge stack loader)
Desk top and rack mount
List $27,000, 94/4/11

There's also a standalone drive with a small autoloader from a company
called Overland Data. Their L490e is a win because it reads and writes
both 18 and 36 track tapes. At $20K it's reasonably priced. For the
www-enabled, see
(, 94/12/21)

Subject: [5.7.1] New IBM Tape (NTP) 3590
From: Tape

Same form factor as 3480, serpentine. 9 MB/sec., 10GB/cart. Bare drive
should retail ~$35K, 1Q95. Two SCSI interfaces? Robotics also
planned. (, 09/30/94)

NTP has been released (95/4/10) as the 3590 tape subsystem with the
Magstar tape drive. The press release didn't mention price,
availability, or interfaces (though it did say attachable to Suns,
RS-6k, etc.).

list price for the 3590 drive is approximately $43.5K;
list for media is approximately $50;
list for 3590 drive + 10 cartridge stacker is approx $48K (95/9/18,

IBM Storage has an excellent WWW page at

Subject: [5.8] Magstar Coyote (IBM 3570) {Brief, New}
From: Tape

There is a second type of tape drive from IBM based on the Magstar
technology. Known as Coyote or 3570, it's 2.2 MB/sec., 5GB in a
two-reel cassette. Unlike 3590, the tape never leaves the cassette.
The width of the tape is much less than 1/2", maybe 1/4"? The
cassette is about the size of an 8mm, give or take. There's an
associated desktop modular autochanger. (rdv, 97/6/5)

Subject: [5.9] QIC {brief}
From: Tape
Quarter Inch Cartridge. Primarily low-end (ie, PC) available from
multiple vendors but 3M is pushing it into midrange market with estimates of
100 Gigabytes per cartridge by 1999. Two-reel cassette.

In Dec '94, 3M, Sony, HP and others announced a new format, 2.3 times
the capacity, available mid-1995. The cartridge and drive mechanics
apparently change. It will be .315 inch tape instead of .25, with 750
feet of media in a cartridge. (rdv, 94/12/16)

Subject: [5.9.1] Travan
From: Tape

Travan is a 3M trademarked name for a new family of data minicartridge
tape media. Travan provides additional capacity via longer
length(750' / 229 meters) and greater width(.315" / 8mm) tape then
previous generations of data minicartridge. Drives that can
accommodate Travan cartridges must have a mechanism that can handle
wider tape (.315" / 8mm vs. earlier data minicartridge that are
.25"/6.2mm) and be able to accept the slightly larger Travan
cartridge. All major drive manufactures have modified existing drives
or designed new mechanisms to accommodate the Travan cartridge.
Today's Travan capable minicartridge tape drive maintains the industry
standard QIC formats. These drives can write and read smaller capacity
data minicartridge tapes of the same QIC format family(See below).

Travan TR1 capable drive functionality
Cartridge Format Capability Native Capacity
DC2120 QIC-80 W/R 120MB
DC2120XL QIC-80 W/R 170MB
QW5122F QIC-80 W/R 208MB
TR1(Travan) QIC-80 W/R 400MB

Travan TR3 capable drive functionality
Cartridge Format Capability Native Capacity
DC3010XL QIC3010 W/R 346MB
QW3010XLF QIC3010 W/R 425MB
DC3020XL QIC3020 W/R 692MB
QW3020XLF QIC3020 W/R 850MB
TR3(Travan) QIC3020 W/R 1600MB


1. TR3 capable drives can read only all combinations of QIC-80 formatted
2. 3M has developed a TR2 800MB QIC3010 format tape but has not gone to
market with it at this time
3. There will be TR4 and greater media products in the future. These
products will offer greater capacity and performance.

(thanks to, aug 16 1995)

Subject: [] TapeStor {brief,new}
From: Tape

The TapeStor 800 and 3200 from Seagate are Travan TR1 and TR3 drives,
respectively, targetted at the home PC market. (rdv, 96/11/4)

Subject: [5.10] 4mm {brief}
From: Tape

Multiple vendors. Initially for home audio market. Original product
held 1.3 GB on one 60 meter tape at about 180 KB/second. Search
speeds run about 200 times nominal speed. DDS (Digital Data Storage)
format has overtaken the DATA/DAT format. Two-reel cassette. gives HP DDS drive information gives specs for the DDS2 C1533A

Subject: [5.11] 8mm {brief}
From: Tape

Sony developed transport designed initially for home video market.
Exabyte has U.S. rights with Kubota qualifying as a second source when

EXB 8200 model holds 2.3 Gigabytes per tape at 220 KB/sec

EXB 8500 model holds 5 Gigabytes per tape at 500 KB/sec

Search speeds of the 8200 is dismal, but is significantly improved in
later models. Compression and half-height (standard is full-height
5.25-inch) features are also available.

See for more info.

Subject: [5.11.1] Mammoth (EXB-8900) {Brief}
From: Tape

Mammoth is the new Exabyte drive. It holds 20 GB
uncompressed per cartridge, with a transfer rate of 3 MB/s. Exabyte
has been touting this drive since at least April '93; it is now
shipping. SCSI-2 fast or fast & wide interface. Read (not write)
compatible with all older Exabyte drives. (rdv,96/11/1)

Subject: [5.11.2] Sony SDV-300 {New}
From: Tape

An article in Computer Tech Review says that Sony has announced a 25GB
native 3MB/sec 3.5" 8mm drive based on the same media technology they
developed for Exabyte's mammoth.

At this point (June 10, 1996), opinions in the newsgroup differ as to
whether or not the _media_ is compatible with Exabyte's Mammoth,
though everybody agrees that SDV-300 will not be read or write
compatible with Mammoth or earlier Exabytes.

Sony's new drive does look impressive. The information that I have
says that production shipments begin this summer (late July for
initial shipments) for units without the data compression feature.
That would be 25GB native capacity @ 3MB/sec. Drives with compression
will ship in 4Q96, for a guess, probably October-ish.

The interesting feature is the NIC cartridge that has positioning
information due out by mid-97 that will eliminate the need to rewind
before unloading the tape and will allow the tape to seek in either
direction on loading. This is a flash chip built into the cartridge

The SDX-300C is apparently one model in this line, already shipping in
some autochangers. No flash index chip yet. (rdv,96/11/4)

(Jeff Johnson (, Bob Covey ( and others,

Subject: [5.12] DLT {full}
From: Tape

See for info on
current issues concerning DLT.

Also see the DLT FAQ, maintained by Larry Kaplan, For Suns, there is info at

Digital Linear Tape (DLT)
TZ87 (DLT2000) - 10 GB native per cartridge
See also robotics (DLT2700 is 7 tape library)
Ref: Digital's Customer Update, March 14, 1994
Serpentine recording.

Developed from DEC's TK50 & TK70 technology. The unit that developed
this was sold to Quantum.

DLT is the new tape technology getting the most air time around here.
There is also a DLT-specific FAQ maintained by Larry Kaplan from

See for specifications, for some FAQ answers. I
also have an old copy of Larry Kaplan's different FAQ available at

From the newsgroup:

Tape uses a special hook for load/unload mechanism.

DEC is the initial vendor, but other vendors are re-selling them
(sort of like TTI's reselling of the Exabyte 8mm tape drive).

Transfer rate of 2.5 MB/sec, but that assumes 2:1 compression, so it
is 1.25 MB/Sec native. Likewise the 20 GB cartridge is 10 GB native.

DLT4000 ($2K upgrade from DLT2000) soon (9/94?) Double the capacity.
Some agreement with Cypher. Still not shipping in quantity, 1/95.

Can be used on NON-DEC systems (standard SCSI interface).

One report of a batch of tapes that were "too wide".

> (Michele Michelotto) wrote:
>You're comparing the top QIC format with the rather new DLT
tecnology. What is so special about DLT? I'll try to answer:

>1. Serpentine format means that there are several parallel tracks.
the head goes down the first track and comes back down the second one
etc. If I need to access a file at the end of the "logical tape" and
the drive knows that it is at the beginning of the 52th track it goes
directly to the 52th track and start seeking on it. So the worst case
access time is close to the rewind time (about 100 sec) the average
access time is about (60 sec).

>2. the unit I tested was a 6 GB/cartridge (no compression) 700
kB/sec. the cartridge had 112 tracks but since the drives use two
heads, it could access track N and track N+54 together. So it looked
like a 54 track cartridge. Now it's very easy to put 4 (or 8) heads in
the drive and double (or multiply by 4) the transfer speed while
maintaing the backward compatibility (with 8 head you use only head #1
and #5 to emulate a 2 heads unit).

>3. DEC is selling to the OEM a DLT4000 unit with 20GB uncompressed
(40GB with compression). [may be available 9/94]. [Thinner, longer
tape plus somewhat higher density and slightly more efficient

DLT cost $5K US for 20GB drive, $10K for a 140GB stacker, $150K for a
3.2 TB robot.

Autochangers are made by DEC, Odetics (available through EMASS) and
Metrum (now MountainGate).

Piping tar into dd, with a bs=64k can increase your speed.

The drives have a tape mark directory that is used for a SPACE
command, but if you just SPACE 1 FILEMARK multiple times, efficiency
is poor (and is the fault of the software implementation as it should

Submitted (approved?) ANSI standard, but that does not mean anyone
other that DEC is doing anything more than OEM'ing it.

Subject: [5.12.1] DLT7000 {Brief}
From: Tape

35 GB on a cartridge (uncompressed), 5 MB/sec. transfer rate. Drives
available in limited quantities now, general availability was
targetted for June/July '96, but still apparently months away? (Alex
Brill,, 1996/2/23, updated rdv, 96/7/8)

Subject: [5.12.2] DLT4000
From: Tape

Streaming tape drive
Quoted 40 GB includes 2:1 compression
Quoted 3.0 MB/sec includes 2:1 compression
Extended 5.25-inch form factor
SCSI-2 interface, either single-ended or differential,
optional fast SCSI.
Compression is DLZ (Digital Lempel-Ziv)
"...a head life of 10,000 hours (compared to 2,000 hours for
other tape products), a recommended average of 10,000 read/writes per
cartridge, and an MTBF of 80,000 hours."
Search speed averages 68 seconds
Repositioning time 1.3 seconds
Hard error rate: 1 x 10**17 bits read
Undetected error rate: 1 x 10**30 bits read
Serial serpentine (128 tracks), variable block
bits/inch: 82,000
Tracks/inch: 256
Recording media: CompacTape (tm) IV
0.5 in x 1,700 ft x .3mi thick
Cartridge: 4.1 x 4.1 x 1 inch
shelf life: 10 years
Height: 3.235 in, width: 5.7 in, length: 9 in
Reliability: 80,000 MTBF
Media reliability: 500,000 passes in start/stop mode (or an
average of 10,000 uses/cartridge)

Subject: [5.12.3] DLT2700 (from DEC)
From: Tape

random access, seven tape, 1 drive library
rack mountable 8-inch form factor
includes operator control pannel and LED indicators
400,000 mean mechanical cycles before failure
uses a 7 cartridge magazine.
Magazine "precheck": 75 seconds per magazine
Cartridge load (max): 28 seconds
Cartridge unload (max): 30 seconds
SCSI command set for robotic commands
Subsystem reliability: 30,000 power-on hours
Height: 10.4 in, width: 8.7 in, length: 27 in
weight: 65 lbs
same as the TZ877?

Subject: [5.12.4] DLT2000 (from DEC (now Quantum))
From: Tape

CompacTape (tm) III
Capacity: 20 GB/cartridge
(assumes 2:1 compression)
1.25 MB/sec. (Rodney D. Van Meter),
(Peter Van Epp),,,

Subject: [5.13] MountainGate (was Metrum) VHS {brief}
From: Tape

800-556-0222 or 702-851-9393 Phone
702-851-5533 Fax
in Europe: Mountaingate Data Systems Linda Radley in the UK
+44-1256-464-767 (tel) +44-1256-597-48 (fax)
Drive: RSP-2150, 2MB/sec sustained, 4MB/Sec burst
ST-120 cartridge holds 14.5 GB
ST-160 cartridge holds 18 GB
See also robotics

Integrated with lots of SW packages, and drive prices have come way
down. I think you can now get them for less than $15K. Integrates
smoothly with robotics.

See for one
performance evaluation. Lots of good info there, but keep in mind that
the testing was conducted in 1992.

Subject: [5.14] VCR VHS
From: Tape

This appeared recently in the newsgroup, but I don't know anything
about it. This is the widget that takes data in one end and spits out
a video signal that you can pipe into your home VCR to use your it for
data storage. It's only $350, but, for those of us in the U.S. and
Japan, it doesn't work for NTSC VCRs.

Subject: VTS Tech Specifications for Users
Date: Mon Nov 28 09:24:29 PST 1994

Having received a lot of questions from different users of VTS 1020,
I'd like to answer them giving short specifications of this unit.
1. CAPACITY: 4 GB Compressed / 2 GB Uncompressed on one E-180 cassette.
The amount of data grows according to the tape length.
2. SPEED: 100 KB/sec for PC/AT 286-16 Mhz
200 KB/sec for PC/AT 386-33 Mhz etc.
3. SOFTWARE: The current version is for DOS. Windows support-DOS Window.
Read/Write verification is provided.
4. VIDEO: PAL/SECAM System, VHS Tape

Also from the newsgroup a while back:

We, AT Systems Inc., are distributors of VCR cassete backup kits
(including PC board and software package with 1 year warranty and 2
weeks money back policy), please send all inquiries to my e-mail
address (Michael V. Kuzmin,, 4/95)

And more recently:

Check out a company call Cybernetics in Yorktown, Virginia. They
put Sony VCR drives in their own enclosures for backup devices.
Contact Thomas Dougherty at (804) 833-9000. (Mike Rothenberg,, 1996/4/1)

Subject: [5.15] 19MM (D1 and D2) {Brief}
From: Tape

19mm is 3/4 inch helical scan tape. Two varieties exist, D1 and D2.
Both originated from broadcast and/or data recorder applications,
where the data/signal was analog in nature. They have been modified
for digital use, with error correcting capabilities added.

Data rates are in the 8-45 MByte/sec range, with storage capacities
in the 25-175 GB range in physically different size cartridges with
different length tapes, but all fitting into the same tape drive unit.

Subject: [5.16] ID-1
From: Tape

SHMO: I'd like to hear more of people's experiences using these

Note: I would recommend you talk to people who've used these things
before buying one!

Subject: [5.16.1] DATATAPE
From: Tape

DATATAPE (Pasadena, CA, formerly a division of Kodak), has an ID1
system available, with a HiPPI interface. You can find more info and
even give them design feedback at The
DCTR-LP400 goes up to 50 MB/sec., the fastest single general-purpose
tape drive I know of. Reachable by phone at (818)796-9381 (rdv, 96/8/7)

Subject: [5.16.2] Sony
From: Tape

Sony makes several models of a D-1-based data drive; the format is
generally referred to as ID-1. It comes in different models, with
equivalent price tags, that run from 8 to 32 MB/sec. The original
machine had a VME interface that was extremely low-level ("any lower
and you'd have to turn the spindles by hand," someone said); now there
is a HiPPI interface available from a company called TriPlex. I
understand the HiPPI interface also adds another layer of ECC to
improve the otherwise abyssmal error rate (10^-10 becomes ???). Sony
is also supposed to be doing their own SCSI and HiPPI interfaces. I
don't know the status nor if they are compatible with tapes from the
TriPlex unit (I suspect not).

SONY has announced 3 interfaces so far. ;-)

DFC-1500 - SCSI interface

DFC-1700 - FW-SCSI-2 interface

DFC-1800 - 8 bit ECL interface that acts as a "scrollable" buffer.

All of the interfaces are fully buffered. They list for 40K-88K.

I have used the DFC-1700 for some time. From the standpoint of SCSI
functionality it is quite good. It obeys the MT commands and if you wish
you can either write to it in "raw" mode or DTF, which is SONY's version
of the DD-1 spec. On an HP I get 14+MB/Sec on the DTF side and near 16MB
in RAW mode.

TriPlex makes an interface that does SCSI,FW-SWCI-2 and HIPPI. The price
varies. List for the HIPPI version is in the $130K range. The controller
is fully buffered.

Myriad Logic also builds boards (VME) and a controller. The controller
was demonstrated in Europe this year. It is a HIPPI attached controller
built out of their existing products. No good feel for the price, but I would
GUESS that it will be less than 90K. It is also fully buffered with 384MB
of VSB memory.

These are very expensive -- $100K+, but for people with the need,
they've got the speed.

(, (John Stephens), (Rod Van Meter), (stephen w. poole) (8/95))

Sony's sales literature now (1996/3/22) says they plan to introduce a
64 MB/sec. drive "in the near future". (rdv)

Subject: [5.17] D-2
From: Tape

Ampex supports D2. Data rates are in the 15 MByte/sec range.

The Ampex tape transport and head system were originally sold through
E-Systems (EMASS), who built the storage controller and sold it as the
ER-90 and coupled it with Odetics robots. Ampex now makes their own
interface for the unit, sold as the DST. They also make their own very
fast robotics.

The ER-90 is popular with the oil crowd. I don't know if the tapes are
interchangeable with the DST.

(rdv, 12/94)

DD-2 (19mm Data D-2 Format)

Ampex DST General:

3 cartridge (cassette) sizes - 25, 75, 165 gigabytes (uncompressed).
15 megabyte/sec. sustained (20 megabyte/sec. burst) transfer rate (per
drive). Up to 800 megabyte/sec. search speed (per drive). Smart DD-2
format includes partitioning and system zones to maximize storage
efficiency and speed data access. 3 layers of Reed-Solomon error
correction, with read-after-write verification and automatic rewrite
yield error rate of 1 in 10E15 bits read. Drive(s) dual ported SCSI-2
(16 bit fast, differential).

DST 310 Tape Drive:

All 3 cartridge (cassette) sizes supported - 25, 75, 165 gigabytes
(uncompressed). Rack mount or table top configurations. Single unit
price: $120K.

Ampex recently (dec. '95 or thereabouts) announced a new tape drive
model that's substantially cheaper, ~US$80K. Still 15 MB/sec., but I
think it only supports S cassettes.

Ampex Corporation
401 Broadway, M.S. 3-46
Redwood City, CA 94063-3199
Inquiry: 415-367-2982
Facsimile: 415-367-3850

(see also Ampex under autochangers -- they make their own for this
tape drive)

(, 94/12/23)

Subject: [5.18] StorageTek Helical {Brief}
From: Tape

Storage Tek has been working on a project called Redwood for a number
of years. The cartridge will be 3480 form-factor, to protect users'
investment in Storage Tek robotics. ( (Rod Van
Meter)) Cartridges come in three lengths, with capacities of 10, 25
and 50 GB. That would put one of their 6,000-cartridge silos up to 300

The ESCON interface is in betatest; SCSI fast & wide due out soon.
(, 94/12/19)

Reportedly available now (95/5/15) with the SCSI interface; ESCON has
been delayed until end of the year.

Sustained transfer rate of 11.25 MB/s. Supports compression. List
price ~$100K.

Compatible with most of the STK robots. See and
also autochangers in part 2 of this FAQ.

Subject: [5.19] Optical
From: Tape

A company called Creo, from Canada I believe, makes a large tape drive
that uses ?1"? tape and gets a terabyte of data on a $10,000, 880
meter reel. The time to read the media (media granularity) is huge;
at 3 MB/sec. it takes almost four days to read a tape!

EMASS have aquired the rights to manufacture the optical tape drive
from CREO. The drive ($350k) provides 1TB on line with data transfer
at 3MBytes/sec and an average seek time of just 30 seconds. Optical
tape media is supplied on 12.5" reels (capacity 1 TByte) by ICI
Imagedata in the UK. Expected archival life 30yrs. Typical price of a
reel is $8,500. (updated 1995/9/18,
has some info.

Subject: [5.20] D-6 {brief}
From: Tape

From Toshiba & BTS, originally designed as a full-speed (~150MB/sec.)
digital HDTV VTR. A model with a HiPPI interface is supposed to be
available end of 94. The video version is priced at US$300K+. I
believe the tape transport and cartridge are the same as for D-2,
though the tape material is different.

(4/94, rdv)

Subject: [5.21] D-3 {brief}
From: Tape

From Martin Marrieta, mentioned here on the net recently. Very fast
(10.8 MB/sec.), ~$125K. General availability scheduled for 11/14/94
(9/20/94, I believe the cartridge is the same as
Betacam, so look for the broadcast autochanger companies here (rdv).

Subject: [5.22] Sony DTF {Brief}
From: Tape

Sony DTF is also a helical scan device, utilizing 1/2" digital data
cartridges, same form factor as Digital Betacam. Capacitities of 12
(small cartridge) and 42 Gigabytes (large cartridge) UNCOMPRESSED at a
sustained transfer rate of 12.2 MB per second again UNCOMPRESSED with
and error rate of 10 to the -17. MTBF 200,000 HRS.

INLINE sells this as the INLINE RES-400. Cost $55,000 per transport
with 16-bit SCSI differential interface.

800.465.4637 or 703.478.0800 main, 703.478.0966 fax

(John Tibbitts,, Oct. '95)

Also available from Cybernetics, EMASS, Transitional Technology here
in the U.S. and several others in Europe and Asia (contact rdv if
you're interested in contacts). One of these makes an SBCON interface
for the drive. No Fibre Channel or HiPPI yet that I know of. Not
available directly from Sony.

(updated rdv, 1/96)

Subject: [5.22.1] GY-2120 {New}
From: Tape

Sony introduced the GY-2120 DTF tape drive in March of 1997. This is a
re-engineered version of the first DTF drive, GY-10D. It is now a one
piece, smaller and lighter version with added features. Best of all,
the new suggested list price is $31,000.00.


12 MB/sec sustained data rate
up to 20 MB/sec w/compression
42 GB Native Capacity
108 GB w/compression
ALDC High Performance Compression, Average ratio 2.59:1
Automatic Head Alignment
Automatic Head Cleaning system
Automatic Tape Cleaning system
300 MB/s Search Rate
Fast Unload/load of < 25s
Head Life > 5,000 hrs
MTBF: > 200,000 hrs
Read/Write Passes: > 20,000
Tape Archive Life: up to 30 years

Distribution has changed as well, we now sell to VAR's and through
Sony's Broadcast Division in addition to OEM's:

OEM's: Cybernetics
Precision Echo

VAR's: Ovation Data Services
Performance Group
RFX, Inc.

( (Wes Kuch), 1997/6/24)

Subject: [5.23] DATATAPE DTR-48 {Brief}
From: Tape

In addition to their ID-1 tape drive, DATATAPE makes a 1/2" tape drive
called the DTR-48, 6 MB/sec., 35 GB on a cartridge. I believe the
cartridges are the same physical form factor as Betacam. (rdv, 96/8/1)

Subject: [6] Disk
From: Disk

Subject: [6.1] CAV, ZCAV and CLV
From: Disk

Many disks (hard, floppy and optical) run in CAV (Constant Angular
Velocity) mode. In this case, the disk spins at a constant rate, and
there are the same number of sectors per track on inner and outer
tracks. This means that the bits are farther apart on the outer
tracks, potentially wasting space. The transfer rate is
constant, as the number of bits/track is same and the time/track
doesn't vary.

CDs (and video laser disks, I believe) and early Macintosh floppies
run at Constant Linear Velocity (CLV). That is, the bits are all
roughly the same size, and the rotations per minute of the drive is
adjust as the head moves in and out. This gives the best areal
density of bits, at the sacrifice of seek speed, since every seek
requires an adjustment of the rotation speed. The transfer rate is
constant, as the size and spacing of bits is constant and the linear
velocity is constant.

The current rage is ZCAV, Zoned Constant Angular Velocity. Most modern
SCSI disks have this feature, and the newest MO drives do, as well.
There are a number of zones defined on the disk. The number of sectors
per track is different in each zone. Thus, the data is packed more
densely than normal CAV, but seek speed is not sacrificed. Another
effect of ZCAV is that the media transfer rate varies depending on the
head position, because the time/track is constant and the bits/track
vary; for example, the Seagate ST12450W Barracuda drive varies from 68
to 113 Mbits/sec, almost a factor of two different. has a couple of
papers on this topic, and I (rdv) have a paper in consideration for a
conference on the topic (6/96).

Subject: [6.2] Optical {Brief}
From: Disk
See also Robotics section for library options.
Slower than magnetic disks (in general)

Subject: [6.2.1] CD-ROM
From: Disk
Historically produced off-site at significant first-copy cost but
small cost for high volumes. Now on-site 'authoring' systems are available.
Standard formats are available. Ads have been posted to the net
offering services for as little as US$60 to convert a tape to CD.

Subject: [] DVD (Digital Versatile Disk) (Next-Generation CD) {New}
From: Disk

Digital Versatile Disk (DVD), the new standard, is a two-layer
single or double-sided CD, 8.5 or 17 GB, or double-sided single-layer
CD, 9.4 GB. Transfer rate is 11 Mbits/sec (1.4 MB/s). contains a quick overview.
First versions will be read only, later will come WORM, then

First products are slated to be available by the end of 1996.

There were two new standards in the works, digital video disk (DVD)
and high-density compact disk (HDCD). DVD was proposed by 8 major
consumer electronics giants (including Toshiba, with Time-Warner on
board) and would have featured a double sided disk capable of storing
5GB of data per side. HDCD, backed by Philips and Sony, would have
held 3.7GB data, with the potential to double them up to hold 7.4GB by
using a two-layer technology.

VHS/Beta wars all over again, along with issues such as backwards
compatability to existing CDs, were avoided, thankfully. In December
of 1995, everybody agreed on the new DVD format.

See the article by Alan Bell in the July 1996 Scientific American.

(John Wiest (, (Michael Gold) and
others, 95/04/20, rdv, 96/7/1)

My (rdv) notes from the Goddard mass storage conference, 1996:

Mike Wingart, Sony, talked about DVD.

Their data rate is 11.08 Mbps, though video formats are generally used
in a slower mode than that. Two sizes, 8 cm and 12 cm.

size single layer, double layer,
single side double side
8cm 1.4 GB 5.2 GB
12cm 4.7 GB 17 GB

track pitch is 0.74 mm, compared to 1.6 for CD (I wrote mm, but I'm
sure that's microns).

Starts at the inner hub and moves out as it reads the first layer,
when it switches to the second it reverses direction.

They are working for backward compatibility, but the CD-recordable
format uses a dye polymer that's wavelength sensitive; CD-R is 750 nm,
but they are using 650 nm laser.

Movie is only 4.8 Mbps (he didn't explain the discrepancy, but I
presume they just don't use the extra bw). Video is 3.5 Mbps, the rest
is audio (5.1 channels, 3 languages, 4 subtitles).

They run 130 to 472 minutes of video on 12 cm disks.

Using ISO 13346, the volume & file standard for write once and RW
non-sequential media.

Using ISO 9660, the CD-ROM FS std, needs some modification to work?

DVD-ROM spec 1.0 released Sept. 6th, 1996; others coming soon.

Rewritable 2.6 GB single layer requires cartridge to protect disk.
Cyclability of rewritable media is still an issue.

Subject: [] GIANT CD-ROMS {New}
From: Disk

A bit of news that I came across recently:

Norsam Technologies Inc. in Albuquerque, N.M., is developing a CD-ROM
technology that would enable users to store up to 165 gigabytes on a single
disk -- almost 10 times as much data as can be stored on digital video
disks. The additional capacity is made possible by replacing the prevailing
800- and 350 nanometer laser writing technology with a more powerful
50-nanometer particle beam. "The Norsam HD-ROM will ... be a major
competitor in the high-availability data arena," says the company's
president. The HD-ROM disks will be the same size as current CD-ROMs, but
will require users to install high-density readers in their devices.
(InternetWeek 14 Nov 97)

Subject: [6.2.2] WORM {brief}
From: Disk
Standards are less firm between vendors.

For info on file systems for WORM, see the reference to ISO/IEC 13346
in Also check out the OSTA (Optical
Storage Technology Association) specs for UDF (Universal Disk Format).
UDF is one of the file systems that will be used with DVD.
(from and, 1996/3/20)

Subject: [] Sony {brief}
From: Disk

In the July '95 Wired, p. 56, and seen at SIGGRAPH '95:

new Sony WORM drive, looks like 12", maybe bigger. 15GB on a $400
platter. drive is $21K. 76-disk autochanger is $112.5K. ZCAV. transfer
rate 2.7 MB/sec. sustained.

call 1-800-222-7669.


Subject: [6.2.3] Erasable
From: Disk
Better standards than WORM

Subject: [] Magneto-Optical Physics
From: Disk

Magneto-optical disks are plastic or glass disks coated with a
compound (often TbFeCo) that has special properties. The disk is read
by shining a low-intensity laser (originally infrared, but experiments
are being conducted all the way up to blue, I believe; the shorter the
wavelength the higher the possible density, all things being equal
(which they never are)) onto the media and examining the polarization
of the reflected light. To write, a higher-intensity laser is used to
heat the material up to its Curie point, where it becomes susceptible
to a magnetic field. When the media cools again, its state is
"frozen". The polarity of the reflected light during a read depends on
the polarity of the magnetic field under which the media was last
cooled. Once it has cooled it is no longer suceptible to magnetic
fields. Thus, it can be compared in a sense to paleomagnetism.

Subject: [] Sony MiniDisc {Brief,New}
From: Disk

Sony introduced a 2.5" removable cartridge disk drive in 1993 that
will hold 140MB. The rewritable version is magneto-optical; there is
also a read-only CD-like version. Also manufactured by others,
including Sharp, who says it will have a 700 MB version in 1997. Great
info available at or (rdv, 96/7/7)

Subject: [] Magneto-optical, 5.25-inch
From: Disk
Same number of sectors on each track whether or not track is near
center or outer edge. 640 MB. Made by IBM, HP, Sony, Ricoh, others?

Subject: [] Magneto-optical ZCAV, 5.25-inch
From: Disk

Zoned constant angular velocity - more sectors on outer tracks.
GB: 1
ECMA standard 183 going through ISO Fast Track.
ADSTAR demonstrated (6/93), San Jose, CA, 408/256-7895.

Subject: [] HP Corsair {Brief}
From: Disk

1.3 GB on a double-sided cartridge.

See also under MO autochangers in part 2. describes HP products.

Subject: [] Maxoptix T4-1300
From: Disk

Does 1.3, 1.0 (read only) and 650 MB media. Max sustained read 2.0

See also under MO autochangers in part 2 for contact info.

(rdv, 95/02/14)

Subject: [] Pinnacle Micro {New}
From: Disk

Pinnacle Micro ( makes MP drives with
capacities of 650 MB, 1.3 GB, and 2.6 GB, with transfer rates up to 6
MB/sec(!). Reportedly they're developing a 4.6 GB drive (Apex), too.

Pinnacle also makes 10x CD-ROM drives and CD-recordable drives.

(rdv, 96/7/8)

Subject: [] Asaca HSMO {Brief}
From: Disk

My company (Asaca) makes a 12.24 MB/sec. MO drive that uses custom
media and two four-beam heads in parallel to increase the transfer
speed. Expensive.

Call our L.A. office, (310)827-7144

Subject: [] Other Multi-beam MO {None}
From: Disk

Subject: [] 3.5-inch MO {Brief}
From: Disk

Generally looks like a slightly overweight floppy. All current ones
are single-sided.

First generation 3.5 MO was 128 MB on a cartridge.

Second generation devices (available now) are 230 MB.

Third generation (due out this year?) will be 650 MB.

If they bring the drive price down, could displace floppies as the
basic shirtpocket-transportable medium.


Subject: [] Sony {Brief}
From: Disk

Sony now has 650 MB/side 3.5" MO with direct-overwrite capability (a
major step forward in MO). See It's ZCAV, and
nominally 1-2 MB/s. There's a reasonable discussion of MO physics and
technology here, too. ( (Mark Holzbach), 10/95)

Subject: [] Nikon 12-inch MO {Brief}
From: Disk

Holds 8 GB on a disk, with a transfer rate of ?>1MB/s.

Subject: [] Sony 12-inch MO {Brief}
From: Disk

Sony also makes a 12" MO. 3.2 GB? (rdv,95/2/7)

Subject: [] NEC 12-inch MO {Brief}
From: Disk

NEC also makes a 12" MO. (rdv,95/2/7)

Subject: [6.2.4] Electron-Trapping {None}
From: Disk

Subject: [6.2.5] Dual Function {Brief}
From: Disk

Capable of using both WORM and Erasable media. Some do the WORM in
firmware -- the media is really rewritable. Others do true WORM. Some
drives listed elsewhere, such as MiniDisc, support this.

Subject: [] Panasonic/Toray {Brief}
From: Disk

The Panasonic/Toray phase-change drive **READS** CD's but **WRITES**
phase-change discs which are not compatible with CD's and cost as much as
M-O media. (Mike Schuster,, 8/95)

Subject: [] IBM {None}
From: Disk

Subject: [6.3] Magnetic
From: Disk

This area moves WAY too fast for me to keep up with all of the
products and announcements; ideally, it should teach enough about
principles and other information sources to allow users to find the
information they need.

Quantum has a good educational web site, with info on the history and
technology of disk drives, at

A lot of spec sheets for recent disk drives (when they say they also
have "old drives", they mean early 90s, not 50s-80s) is available at Looks like a good site.

Subject: [6.3.1] 5.25-inch
From: Disk

Subject: [] Seagate
From: Disk

Seagate's Elite 9 is 9GB -- reports here of backordering, others of
availability. Micropolis due out with an 8GB soon? (94/9/1)

The fastest (in sustained transfer rate) known 5.25" disk drive is the
ST12450W2HP 1.78GB Barracuda drive from Seagate. The Barracuda family
is large, so pay attention to the model number! It runs at 68-113
Mbits/sec., depending on head position (it's ZCAV). Assuming that data
rate is pre-format, and subtracting 20% for the format overhead, that
would be a sustained rate of 6.8-11 MB/sec. Of course, your mileage
WILL vary according to transfer size, locality, etc. (rdv,95/2/7)

Seagate announced a couple of weeks ago a 23GB disk drive. Reportedly
shipping in summer. (Brian A Berg <>, 1996/3/29)

Subject: [6.3.2] 3.5-inch
From: Disk

Subject: [] IBM
From: Disk

The IBM DCMS-310800 Ultrastar2 is 10.8 GB (1GB=10^9) after format, and
its sustained rate is fast -- 8.4-14.2 MB/sec (presumably pre-format,
so subtract 20%). Only 5400 rpm with an 8.9 msec seek time, so
middle-of-the-pack on those numbers. Fast/wide SCSI-2 interface.

Subject: [6.3.3] Hard Disk Manufacturers {Brief}
From: Disk

Here's a partial list of web pages for manufacturers of disk drives.
At many of these you can get reasonable tech info and support contacts. (Fujitsu) (now merged w/ Seagate)

NOTE: HP announced on about July 10th, 1996 that they're getting out
of the hard disk business. The article I saw didn't give an exact time
frame. (rdv, 96/7/13) has good info on
older drives, and new info is available at

Subject: [6.3.4] Bernouli {None}
From: Disk

Subject: [6.3.5] Floptical {Brief}
From: Disk

I believe flopticals use an optical tracking mechanism to improve
ordinary magnetic head positioning and therefore density.

The Compaq/3M/Matsushita floptical floppies actually hold 120MB
formatted (according to the August 95 Byte), and can read and write
standard 1.44MB floppies and read 720KB floppies. (John Brock,, 8/95)

Supposed to be available Dec. '95?

Subject: [6.3.6] PC Removables {Brief}
From: Disk

SHMO -- I haven't followed this too closely. There's the Zip, Jaz,
and the new SyQuest.

Subject: [] SyQuest EZ135 {Brief}
From: Disk

As of August 1995, $199.00 for the drive, $20.00 for each cartridge
(135 MB). Removable magnetic hard disk. SyQuest has been in the
business for years; the 5.25" removables were popular with Macs.

SyQuest has a new 3.5 inch formfactor removable hard drive (due out
june). 11msec seek time. Their rep tells me it will list for about
$500 and cartridges will come in two flavors:

a) 1.3 gig @ $94 (list) b) 650 mb @ $64 (list)
(, 1996/3/29)

Subject: [] Iomega Zip {Brief}
From: Disk

100 MB/disk, ~$200 for the drive, ~$15-20 for disks. SCSI or parallel
interface, 1.5 MB/sec. transfer rate? Don't know anything about the
technology, I assume it's simple magnetic hard drive. (rdv, 12/95)

I heard that Iomega has licensed the technology to Epson, Fujitsu and
one other maker (rdv, 1996/3/29).


Subject: [] Iomega Jaz {Brief}
From: Disk

1 GB, up to 6 MB/sec. xfer rate for a removable hard disk. Drives are
$600-$700 U.S. and cartridges $150 for 1GB. See
(rdv, 1996/4/10)

Subject: [] SyQuest Removable Cartridge hard Drives
From: Disk

form factor: 2.5", 42MB
form factor: 3.5", 105MB, 14msec ave seek, 3600 RPM, ave sustained
transfer rate: 1.3MB/Sec, available in IDE and SCSI versions. Syquest
Technology, Inc., 47071 Bayside Parkway, Frement CA 93438, Phone: 800/245-

Subject: [] Kalok removable cartridge hard drives
From: Disk

3.5-inch form factor, 250 MB Phone: 408/747-1315 or 408-468-1800

Subject: [6.3.7] Mainframe {Brief}
From: Disk

Mainframe disks are sometimes referred to as SLEDs (Single Large
Expensive Disks). The term DASD (Direct Access Storage Device) usually
refers to a mainframe disk, but is occassionally applied to any hard

The WWW FAQ contains some information about mainframe CKD disks and
file systems.

Subject: [6.4] Other
From: Disk

Subject: [7] RAID {Full}
From: RAID {Full}

The primary functions of a disk array is to increase data
availability, to increase total storage capacity, and to privide performance
flexibility by selectively spreading data over multiple spindles.

Data Protection - As the number of disks on a system increases, the
likelyhood of one failing increases. Thus, a disk array should be immune
from a single disk drive crash. Disk mirroring (keeping an exact copy of a
one disk on another) is the simplest, but requires twice the disk capacity
(and associated cost). Encoding schemes can be used to reduce the redundancy
required to lower ratios.

Storage Capacity is increased by placing many smaller form factor
(5.25 and 3.5-inch) drives onto an intelligent controller which makes all the
drives appear as one drive to the computer system.

Performance can be increased by spreading data over spindles and
performing operations in parallel which allows multiple drives to be working
on a single transfer request.

Subject: [7.1] RAID Levels
From: RAID {Full}

The original taxonomy of RAID levels was published in the SIGMOD paper
by Garth Gibson and Randy Katz in 1988 (see below). The taxonomy
roughly classifies RAID architectures according to the layout of data
and parity information on disks. It is NOT gospel and does NOT cover
every possible architecture (it has been pointed out here that that
would require an N-tuple showing data block addressing, number and
types of parity and ECC information, etc.), but when used properly
provides a vocabulary and establishes a framework for discussion.

Raid Level 0 - Striping - Data is segmented and split onto multiple
Short Reads - Easily handles multiple simultaneous reads
Long Reads - Single operation can be split and processed in
Short Writes - Easily handles multiple simultaneous reads
Long Writes - Single operation can be split and processed in
Redundancy - None
Cost - Good (no extra hardware)
Raid Level 1 - Mirroring - Duplicate data is kept on multiple
Short Reads - Faster (shorter latency) since
resolution can be from any of multiple disks
Long Reads - Faster since resolution can be from any of
multiple disks (*)
Short Writes - Slower since need to write to multiple disks
Long Writes - Slower since need to write to multiple disks
Redundancy - Excellent
Cost - Expensive - at least double the spindle cost
Raid Level 3 - Data protection disk - mathematical ECC type code
calculated from multiple spindles and stored on another spindle.
Short Reads - Normal speed (i.e. 1x per-spindle rate)
Long Reads - Normal speed
Short Write - Slower due to re-calculating of ECC code
(including reading from other spindles and the ECC write)
Long Write - slightly slower due to ECC writes, but less
reading required than in short writes (**)
Redundancy - Excellent
Cost - only slighly more than no redundancy options
Raid Level 4??? similar to 3, with block striping instead of byte.
Raid Level 5 - Striping plus data protection - stripe data across
multiple spindles (as in RAID Level 0) and have data protection calculations
(as in RAID level 3) but don't put all the calculated figures onto one
spindle, but spread it out.
Short Reads - Normal
Long Reads - Faster due to parallelism
Short Write - Slower due to ECC calculation (including
reading and writing)
Long Write - slighly slower due to ECC writes (**)
Redundancy - Excellent
Cost - only slignly more than no reduncancy options

(* should be the same speed as a single spindle)
(** -- should be faster than a single spindle due to parallelism on
write? somebody help me out --rdv)

Benefits of RAID:
High data availability (ie, if a single spindle crashes, no
data is lost)
Increased disk connectivity per system - since multiple
spindles appear as one spindle to the computer system.
Large capacity storage in a small footprint -
Flexibility through intelligent array controllers
Performance enhancements in some circumstances.

Streamed or Streamified RAID??? (SHMO)

Subject: [7.2] RAID-6
From: RAID {Full}

A two-dimensional disk array parity scheme was described by Randy Katz,
Garth Gibson, and David Patterson (all then with UC Berkeley - Gibson is
now a professor at Carnegie Mellon University) at the 1989 IEEE Compcon
conference. This method had one parity calculated along the disk strings
and another calculated across them. This would increase the
mean-time-to-data-loss by more than 10,000 fold. I am not aware of any
implementations of this configuration.

Storage Technology Corp (STK - Louisville, Colorado) has described a
somewhat similar scheme for their long-delayed Iceberg disk array. This
would have a regular, orthogonal RAID 5 parity across drives along with a
Reed-Solomon encoding on another drive. This is sometimes referred to as
RAID 6 or RAID 5+. STK claims their design will allow failure of ANY TWO
drives - which is beyond the survival capabilities of standard RAID 5.

A RAID 5 which is 'deep' can survive failures in more than one drive so
long as it doesn't lose more than one drive per rank:

| | | | | | | |
Rank1 Disk1 Disk2 Disk3 Disk4 Disk5 Disk6 Disk7 Disk8
| | | | | | | |
Rank2 Disk9 Disk10 Disk11 Disk12 Disk13 Disk14 Disk15 Disk16

. . . . . - etc.

Rank4 . . . . Disk32

If the above is a RAID 5 then losing drives 5 & 6 will destroy data. If it
is a RAID 6 then it will not. Losing drives 3 and 12 will not disable a
RAID 5 nor a RAID 6.

But RAID 6 will cost more and may have slower performance for small random
writes from having to update more parity data. I think there are clearly
ways to mitigate the parity update perfomance for RAID 6 as well as RAID 5.

Dick Wilmot
Editor, Independent RAID Report
(510) 938-7425

Subject: [7.3] John O'Brien and RAID-7
From: RAID {Full}

RAID-7 is a marketting term created by Storage Computer, Inc. for what
others here have described as RAID-4 with a write cache. John O'Brien
(, (their marketting manager?) frequently posts

His claims of ~10x improvement on I/O rates for VAXes have been shown
to be poorly measured; the change in systems was not simply a
RAID-for-modern-disk swap, but included increasing the CPU power by a
factor of three and eliminating the HSC and old disk technology. He
has also made difficult-to-substantiate claims about the growth and
market success of his company relative to competitors. Thus, wise
advice would be to take everything Mr. O'Brien says with a grain of
salt (not bad advice for dealing with anyone, but especially true for
dealing with vendors).

The debate also appears here frequently as to whether or not you
really WANT your RAID array doing write cacheing; Unix file systems
may depend on specific ordering of writes and otherwise make
assumptions that could leave you in trouble with power or disk
failures. If write ordering is preserved, the danger is somewhat

That said, some posters here are pleased with their RAID7 arrays, and
although opinion runs prevalently against Mr.
O'Brien himself (and lately his pal Michael Willett who interestingly
is quoted here from before he worked for Storage Computer), the
possibility exists that the product is worthwhile.

Subject: [7.4] RAID Papers
From: RAID {Full}

(Berkeley FTP pointers updated, 95/5/11)

A nice collection of RAID papers was published in the Fall, 1991 issue of
_CMG Transactions_. A few more appeared in the December, 1992 _CMG
Proceedings_ and there are 3 RAID papers in the 1993 International
Symposium on Computer Architecture (Published as _Computer Architecture
News 21_, #2, May, 1993 by ACM SIGARCH.

(, Dick Wilmot, Editor, Independent RAID Report)

There is a short RAID FAQ at (rdv, 96/2/21)

Try contacting the RAID project at the University of California, Berkeley.
In the proceedings of the recent IEEE Mass Storage Symposium, Ann Drapeau
and Randy Katz have a paper describing the reults of some investigations
into the use of tape arrays. I think you can find RAID papers, perhaps
this one, on anon ftp at Have no address for Ann
Drapeau, but Randy Katz is

Some of the RAID papers are available via anon ftp from

Ann Drapeau's email address is

(, Mike DeVaney)
(, Edward K. Lee)

>>I am looking for papers or technical papers on RAID...

You could get that lengthy RAID taxonomy research report from Storage
Computer as mentioned recently on these news groups, by Emailing them at Alternatively, their phone number is 603 880 3005.
I do not know if their RAID research report is copyrighted or not.

I believe their executive in charge of RAID activities in Hong Kong would be
John Taylor, the former Wang national accounts director. They also put
on technical raid seminars which might be of interest to your PhD students,
concentrating on performance enhancements over RAID 3/4/5 (somewhat less than
an order of magnitude, but I have not reviewed their benchmark data.) The
RAID theory discussed is rather interesting.

(MICHAEL...@OFFICE.WANG.COM, Michael Willett)
>> I am looking for papers or technical papers on RAID or other multiple disks
>> storage systems. Could somebody give me pointers for them?

Here are some papers that I either have read or am looking for:

I don't have copies of this group:

Dishon, Yitzhak; Lui, T.S.; Disk Dual Copy Methods and Their Performance;
FTCS-18: Eighteenth International Symposium on Fault-Tolerant Computing,
Digest of Papers p 314-318

Gray, J.N. et. al., Parity Striping of Disk Arrays: Low Cost Reliable
Storage With Acceptable Throughput, 16th International Conference on
VLDB (Austrailia, August 1990)

Katz, R.H.; Patterson, D.A.; Gibson, G.A.; Disk System Architectures for
High Performance Computing; Proc. IEEE v 78 n 2 Feb 1990

Muntz, Richard R.; Lui, John C.S.; Proformance Analysis of Disk Arrays
Under Failure; Proceedings of the 16th International Conference on Very
Large Data Bases (VLDB); Dennis Mcleod, Ron Sacks-Davis, Hans Schek
(Eds.), Morgan Kaufmann Publishers, Aug 1990 pp 162-173

Ng, Spencer; Some Design Issues of Disk Arrays; Compcon '89: Thirty-Fourth
IEEE Computer Society Internationsl Conference p 137-142

Ng, Spencer W.; Improving Disk Performance via Latency Reduction; IEEE
Transactions on Computers v 40 1 Jan 1991 p22-30

Reddy, A.L. Narasimha; Banerjee, Prithviraj; Performance Evalutaion of
Multiple-Disk I/O Systems; Proceedings of the 1989 International
Conference on Parallel Processing p 315-318

Here are some good papers on disk arrays with emphasis on RAID:

Chen, Peter M.; Gibson, Garth A.; Katz, Randy H.; Patterson, David A.;
Evaluation of Redundant Arrays of Disks Using an Amdahl 5890; 1990 ACM
SIGMETRICS Conference on Measurement & Modeling of Computer Systems p 74-85

Chen, Peter M.; Patterson, David A.; Maximizing Performance in a Striped
Disk Array; Proceedings of the 17th IEEE Annual International Symposium on
Computer Architecture p 322-331

Chen, Shenze; Don Towsley; Performance of a Mirrored Disk in a Real-Time
Transaction System; 1991 ACM SIGMETRICS Conference on Measurement &
Modeling of Computer Systems p 198-207

Chervenak, Ann L.; Katz, Randy H.; Performance of a Disk Array Prototype;
ACM SIGMETRICS 1991 Conference Proceedings p 188-197

Menon, J.; Mattson, R.L. and Spencer, N.; Distributed Sparing for Improved
Performance of Disk Arrays; IBM Research Report RJ 7943 (Jan. 1991)

Patterson, David A.; Chen, Peter; Gibson, Garth; Katz, Randy H.;
Introduction of Redundant Arrays of Inexpensive Disks (RAID); Compcon 1989:
Thirty-Fourth IEEE Computer Society International Conference
p 112-117

Schulze, Martin; Gibson, Garth; Katz, Randy; Patterson, David A.; How Reliable
is a RAID; Compcon '89: Thirty-Fourth IEEE Computer Society International
Conference p 118-123

(, Dan Jones)
>>I am looking for papers or technical papers on RAID...

A good set of the Berkeley papers are available via anonymous FTP.
If I remember, the machine was Also, an archie
search on "RAID" would probably turn up a nice on-line collection of
information. (sorry, not at an Internet site to check this right now...)

( , Lester Buck)

Further Information:
%A Garth Gibson
%A Randy H. Katz
%T A case for redundant arrays of inexpensive disks (RAID)
%C Proc. SIGMOD.
%c Chicago, Illinois
%D 1--3 June 1988
%P 109 116
%k RAID, disk striping, reliability, availability, performance
%k disk arrays, SCSI, hardware failures, MTTR, MTBF
%k secondary storage
%L Jacobson has a copy
%x Increasing the performance of CPUs and memories will be
%x squandered if not matched by a similar performance increase in
%x I/O. While the capacity of Single Large Expensive Disks (SLED)
%x has grown rapidly, the performance improvement of SLED has been
%x modest. Redundant Arrays of Inexpensive Disks (RAID), based
%x on the magnetic disk technology developed for personal
%x computers, offers an attractive alternative to SLED, promising
%x improvements of an order of magnitude in performance,
%x reliability, power consumption, and scalability. This paper
%x introduces five levels of RAIDs, giving their relataive
%x cost/performance, and compares RAID to an IBM 3380 and a
%x Fujitsu Super Eagle.


Subject: [7.5] R-Squared {Brief}
From: RAID {Full}
Vangard Disk Array for DEC, Sun, HP, IBM RS/6000, SGI and others

Address: 11211 E Arapahoe Rd., Suite 200, Englewood, CO 80112

Phone: 303/799-9292, Fax: 303/799-9297

Subject: [7.6] Sun {Brief}
From: RAID {Full}

Sun Microsystems has a new Fibre Channel array that does RAID 0, 1,
and 5. See http://WWW.Sun.Com under the products descriptions.

Subject: [7.7] Clariion {Brief}
From: RAID {Full}

See A division of Data General. Mostly big
systems, I believe.

Subject: [7.8] BayDel {Brief, New}
From: RAID {Full}

Targetted at Unix systems -- Sun, HP, SGI, etc. See Fairly big vendor, I'm told. (rdv, 97/3/18)

Subject: [7.9] the RAIDbook {Brief}
From: RAID {Full}

The RAIDBook, a 100+ page tutorial on RAID technology and the
RAID Advisory Board, is available from Technology Forums, LTD,
of 6931 Glenview Lane, Lino Lakes, MN 55014-1296.

Contact Joe Molina, President of Technology Forums at <XXX> (phone
numbers no longer valid?) (rdv,97/3)

I've read it, it's decent but a little repetitive. Defines many
low-level terms of interest only to those who need to know the
internals. (rdv,95/2/7)

Subject: [7.10] Software Striping {Brief}
From: RAID {Full}

Silicon Graphics provides software striping of SCSI disks; thus your
host can effectively act as a RAID controller, providing flexibility
and probably reduced price, possibly with a performance penalty in the
form of increased CPU overhead. However, it probably means that it can
spread the I/O load over multiple I/O controllers.

(similar features in other systems? SHMO --rdv)

RAID0 is in late beta under Linux. ( (Gjoen
Stein), 95/10/6)

sdsadmin on the HP 7xx line does raid 0 striping and works well.
this is also apparently possible on the 8xx machines using LVM.
sdsadmin is due to disappear with hpux 10, replaced by LVM.

I believe the Advanced FS on Alphas can also do raid 0.

(mark hahn,, 94/11/17)

ATTO Technology has ExpressStripe, which does software striping on a

Cyranix makes EZRAID PRO (RAID 0,1,4,5) for
OS/2. Voice: +1 613 738 3864 Fax: +1 613 738 3871

Subject: [7.11] RAID Vendors
From: RAID {Full}

RAID vendors come and go quickly, OEM each other's equipment, change
names, and other activities that seem aimed at simply obscuring the
market. No list like this could be complete and up to date for long;
I'll gladly take updates.

See for one good list of RAID vendors, and for another.

Other reviews are available at, and (
(Steven Hessing), 1996/3/30)

The November '94 issue of _Advanced Imaging_ has a big article on
storage, primarily RAID arrays, with a pretty comprehensive list. This
table is distilled from that. Most of the info appears to be from the
vendors themselves. Almost all of these are fast/wide SCSI; a few are
Fibre Channel, NuBus, PCI or HiPPI (usually with IPI-3 command set).
Most of these vendors have more than one model, only a few are listed
here. (rdv,95/1/18)

Most of these have some web presence; a Lycos search would turn up
their sites.

PC = Personal Computer (IBM compatible)
MC = Macintosh
PS = PC Server (Netware, NT et al)
NT = Windows NT
UX = Unix (generic)
PU = Personal Unix
WU = Workstation Unix & workstation servers
MF = mainframe
MI = minicomputer (AS/400)
SU = Supercomputer

FC = Fibre Channel interface (usually SCSI command protocol)

Maker Model RAID Levels Uses
AC Technology Concorde 0,3,5 WU
ADJFILE Systems Cougar, Tiger 0,1,3,5 ??
AT&T Global Information Series 3 ?? WU,PS,PC
Systems -- NCR
BusLogic DA-x988 0,1,3,5 PC,PU,PS (PCI)
Canary Communications IDA3500 0,1,3,4,5 ??
Ciprico 6800 Real-Time ?? ??
RAID Array
Cybernetics Xtreme 0 ??
DEC StorageWorks 0,1,5 ??
RAID Array 210
Distributed Processing SmartRAID 0,1,5 PC,PU,PS
DynaTek Automation AddARRAY 0,1 ??
Fujitsu Comp. Prod. DynaRAID ?? ??
FWB, Inc. SledgHammer*FT 5 MC
IBM Storage Systems 7137 Disk Array 0,5 WU
Legacy Storage Systems SmartArray ?? PC (PCI)
Maximum Strategy Gen5 Storage 0,1,3,5 SU (HiPPI,FC)
Mega Driver Systems MR & MK Series 0,3,5 PC,PU,PS,MC,WU
MicroNet Technology RAIDbank Plus 0,1,5 PC,PS,MC,PU?
Microtech Int'l XLerator 0,1 MC
Mylex DAC960S 0,1,5,6?,7? ??
Procom Technology LANForce-5 0,1,3,5 MC,??
Raidtec FlexArray IX 0,1,3,5 ??
Recognition Concepts RDR series ?? ??
Storage Computer RAID 7 7?(4?) ??
Storage Concepts Concept 910 ?? ??
Storage Tek Iceberg ?? MF
XL/Datacomp 9638 5 MI,WU

Subject: [8] Solid State Disk (SSD) Frequently Asked Questions (FAQ)
From: Solid State Disk (SSD) Frequently Asked Questions (FAQ)

*Note: This section is a slightly trimmed and editted version of the
SSD FAQ from Robert at DES ( which I think
he also posts to c.d.sybase. I would take the "up to 1000 times
faster" claim with a grain of salt, though the general info is good.
--rdv, 94/9/15

1) Q. What are solid-state disk emulators?

A. Simply put, solid-state disk emulators are Dynamic Random Access
Memory (DRAM)-based storage devices that appear to the host exactly as a
magnetic rotating disk. DRAM chips, which are ultra-fast devices
that store data while the system is on, increase data access, thereby
eliminating I/O bottlenecks that constrain overall system performance.

Solid-state disk emulators can be either volatile or non-volatile,
meaning that they are able to retain data when the system is turned off.
DRAM alone is volatile. Solid-state disk emulators that are designed with an
integrated backup system are non-volatile storage devices; if a power
outage occurs, the user's data is protected by the backup system and will
not be lost. Solid-state disk emulators are volatile when methods for
backing up data are absent. A power failure will cause data to be
lost on a volatile solid-state disk.

2) Q. How do solid-state disk emulators work?

A. Solid-state disk emulators plug into a computer's I/O controller.
Typical client/server systems use the ANSI-standard SCSI interface on
its I/O controller. It is plug-and-play because it emulates a
rotating disk. No special drivers or operating system patches are
required to make it work. In addition, because there are no moving
parts, seek and rotational latency times are zero, which aids
solid-state disk emulators in performing up to 1000 times faster than
magnetic rotating disk drives.

3) Q. What applications are well-suited for Solid State Disk?

A. In general terms: 1) transaction processing, 2) batch processing, and
3) query or decision support analysis. Many types of application
software can take advantage of the super-fast access times SSD offers.

4) Q. How reliable are Solid State Disks?

A. Based on real world user data from a large SSD site, the actual power
on hours mean-time between failure is greater than 1,000,000 hours. Since
this site has yet to have a failure, the number is likely to go up.

Subject: [9] Other Devices
From: Other Devices

Subject: [9.1] Holographic Storage Products {Brief,New}
From: Other Devices

Holoplex is a startup company doing holographic memories. Info on the
web at They reportedly have a
100-image store available as a product. (rdv, 96/7/23)

Tamarack Storage Devices, Inc, a spin-off from Microelectronics and
Computer Technology Corporation (MCC), is developing with Projectavision Inc.
to produce a product with ten times greater storage densities than magnetic
and 10 to 1000 times faster than floppies, tapes, and CD-ROMS. First
products expected first quarter 1994.
(Ref: MCC Collagorations Newsletter, Volume 3, No. 1; Spring 1993)


Note: obviously Tamarack hasn't changed the storage world yet; anybody
know how they're doing? They were awarded another $10.7M by ARPA in
1995 for continued research, but I can't even find a web page for
them. (rdv, 96/7/23)

Also another report of experiments at Stanford recently (8/94).

Scientific American in the Nov. 95 issue reportedly has an article
about holographic storage, but I haven't tracked it down yet.

BYTE Magazine - April 1996
Good Cover Story on "Holographic Storage"

The trade journal "Data Storage" for May/June 1996 had an article
on holographic storage.

Reportedly there is work going on at Georgia Tech on 3-D liquid
crystal data storage, producing a possible gain of 3 orders of
magnitude. (rdv, 1996/3/29, from HPCWIRE)

Subject: [9.2] TeraStor {Brief, New}
From: Other Devices

Big splash and a bunch of announcements March '97. Apparently they've
developed a technique for putting the laser optics for a
magneto-optical drive onto the slider for a regular magnetic head,
giving better density to MO products. Company's still young and needs
lots of people, but it's experienced storage guys. I think their
suggestion that they'll have products in early '98 is probably
optimistic. See (rdv,97/3/18)

Subject: [10] RAIT (Redundant Arrays of Inexpensive Tape)
From: RAIT (Redundant Arrays of Inexpensive Tape)

There are several tape array products on the market:

Data General is selling the CLARiiON Tape Array Subsystem comprising
between five and seven 4mm DAT tape drives. Data can be recorded in
RAID-like striping redundancy, mirrored, or in conventional DAT layout.
This unit can provide up to 30GB of unattended contiguous storage. The
tape drives can record at sustained rates of 183 - 732 KB/second each but
customers should expect sustained backup at around 1 megabyte/second of
compressed data after accounting for host overheads. Data General is
working on a seven tape caddie to hold tape sets together. It is essential
that tapes in a RAID group not be separated.

NCR announced a tape array software product for NCR uniprocessors and
System 3450, System 3550 and StarServer Systems running UNIX V R4.2.01.
This tape array software yields faster and more reliable backup of large
database and file servers than with any single tape drive available today
but uses customers existing tape devices. It writes simultaneously to
multiple drives and can use array techniques to recover from loss or
failure in any single tape.

The motivations for tape arrays seems to parallel those for disk arrays:
- higher bandwidths
- increased reliability

(, Dick Wilmot, Editor, Independent RAID Report)

Pick up any DEC related trade rags and you can find an ad for an 8mm tape
array. The ad I just found is by Contemporary Cybernetics and uses two
five GB 8mm drives with compression - they CLAIM to be able to get 50 GB os
storage total - but how many customers have 50 GB worth of 5:1 compressible

Anyway - the ad doesn't mention RAID, but they support RAIDish (!) features
such as striping and mirroring. It also supports offline tape-to-tape
copy and will automatically cascade onto the second tape when the first
one fills (useful for utilities that can't deal with multi-drive/multi-

I SEEM to remember someone having something like this with more drives, but
of course I couldn't locate the ad.

I would be really interested in seeing something like this for 3480 since the
transfer rate is already quite high...

(, Tom Bodoh)

At the Monterey IEEE Mass Storage Conference in April '93, Ann Drapeau
from Randy Katz's group presented a paper on striped tape.

The National Storage Lab High Performance Storage System reportedly
supports striping of removable media in the system software.


Something that came through the newsgroup recently (95/2/5):

Tape Arrays
High Performance tape drive units for large networks and minis.
Fast: up to 4Megabyes/second
High Capacity: from 24Gb on 4mm DATS to 60GB on DLTs; with
autoloaders,up to 616GB
Flexibility: Stripe data across 4 drives, mirror data,
stripe 2/mirror 2 - double your speed while creating an off-site
storage copy; off-line copy; pass-thru mode, etc.
Transparent to your backup software - no changes or retraining
Compatible with all major OSs; including Novell, WindowsNT,
Unix, Sun, HP, Silicon Graphics, VMS, etc.
For More information:
William Wirth

Just spotted this in a PC rag. Andataco can stripe, mirror or RAID
DLT, 8mm or 4mm. Check out or call
800-334-9191 or +1-619-453-9191. Or email
(Andataco is an integrator for numerous storage products including
RAID arrays.)

Compaq now has a DLT tape array. Some specs available at Stripes or does RAID 5. (rdv, 96/4/17)

Tecmar makes a tape array with up to 30 (custom) drives. A "rotating" spare is
used to gradually back up the entire system. (Georg Feil,,, 96/10/17)

Subject: [10.1] DataVast (was VastNSS)
From: RAIT (Redundant Arrays of Inexpensive Tape)

Originally developed at our institute for use in radio astronomy, the
DataVast is now being built and marketed by DataVation.

DataVast is an SVHS tape array with up to 30 tape transports and a
capacity of 50 GBytes uncompressed per tape (1.5 TB total with 30
transports). DataVast is best suited for near-line networked
applications. It sits on an Ethernet network and acts as an NFS file
server. An internal 4 GB disk serves as a cache for recently accessed
files. Except for the fact that files often take longer to access, the
system appears exactly like an extremely large disk.

File "seek" times depend on user access patterns and file sizes, but most
users can expect average access times under 1 minute and worst-case access
times under 3 minutes. Data transfer rates are comparable with typical
Ethernet NFS servers.

DataVast is not redundant in the sense of a RAID -- the array
architecture is used to increase capacity and reduce cost (the main
electronics is replicated only once for up to 30 tape transports,
unlike SCSI RAIT systems where each tape drive duplicates all
electronics). There is no robotics.


VastNSS is Vast Network Storage Server. This was known as VastNSS,
owned by Legacy, but some of the guys split and bought the technology
and founded Datavation, and renamed the product DataVast. (rdv,
97/3/18) (info updated courtesy of Michael Mansell,, 97/3/18)

Subject: [11] RAOT (Redundant Arrays of Other Things :-)
From: RAOT (Redundant Arrays of Other Things :-)

Pinnacle Micro has been advertising what they call the Orray --
essentially RAID done with removable magneto-optical disk drives. They
claim sustained transfer rates up to 8 MB/sec., which seems
implausible given that it's only four drives, and even HP MO drives
are below 2 MB/sec. sustained. Apparently no redundancy in the system
for that configuration (so I guess my ROAT designator is a misnomer),
but it should be generally less necessary for MO than magnetic disk
(drive failures normally don't result in the destruction of data or

--rdv, 94/7/20

Rodney D. Van Meter

Jan 17, 1998, 3:00:00 AM1/17/98

Archive-name: arch-storage/part2
Version: $Header: /nfs/yelo/rdv/comp-arch-storage/faq/RCS/FAQ-2.draft,v 1.37 98/01/16 18:20:09 rdv Exp $
Posting-Frequency: monthly

Rod Van Meter, Joe Stith, and the gang on

Information on disk, tape, MO, RAID and SSD can be found in part 1 of

the FAQ. Part 2 covers file systems, hierarchical storage management,
backup software, robotics, benchmarking, MTBF and miscellaneous

1. Standards
1.1. ANSI X3B5 {None}
1.2. IEEE Mass Storage System Ref Model (OSSI) {Brief, 6/1/95}
1.3. ECMA - European Computer Manufacturers Association {None}
1.4. System Independent Data Format (SIDF)

2. I/O Related Email Lists

3. Hierarchical Storage Management
3.1. Unitree {Brief}
3.1.1. Epoch vs Unitree
3.2. National Storage Lab {Brief}
3.3. HIARC {New}
3.4. Epoch (also known as StorageTek's NearNet) {Brief}
3.5. Zetaco/NETstor {Brief}
3.6. R-Squared Infinity IFS 2 {Brief}
3.7. AMASS
3.8. Tracer XFS {None}
3.9. Metior
3.10. NAStore {Brief}
3.11. DMF {Brief}
3.12. FileServ {Brief}
3.13. Cray Research's Open Storage Manager {Brief}
3.14. T-mass {None}
3.15. HP OpenView OmniStorage
3.16. Platinum NetArchive-HSM {Brief, New}
3.17. Large Storage Configurations {Brief,New}
3.18. Unix HSM Vendor List
3.19. Mainframe
3.20. PC & PC Server Oriented Packages
3.20.1. HP Optical Jukebox Storage Solution
3.20.2. Chili Pepper Software
3.20.3. Cheyenne ARCserve
3.21. DATMAN {Brief}
3.22. Windows NT
3.23. Other Non-Unix HSM
3.24. Tapes as Disks {Brief, New}

4. Backup Software
4.1. PC-Oriented Backup Packages
4.2. Unix Packages
4.2.1. Spectra Logic Alexandria
4.2.2. ADSTAR Distributed Storage Manager
4.2.3. NetWorker
4.2.4. BudTool {Brief}
4.2.5. HP OmniBack II {Brief, New}
4.2.6. Workstation Solutions {Brief}
4.2.7. Amanda {Brief, New}
4.2.8. Remote Backup or Mirroring {Brief, New}

5. Tape and Autochanger Management Software
5.1. REELlibrarian
5.2. ANT Medium Changer
5.3. Tapes 3000 {Brief}
5.4. Others

6. Robotics (Autochangers, Jukeboxes, Stackers, Libraries)
6.1. 8mm {Brief}
6.1.1. Exabyte {Brief} EXB-10h EXB-210 EXB-220 EXB-440/480 EXB-10 EXB-10i EXB-10e EXB-120
6.1.2. ADIC {Brief, New}
6.1.3. Storage Tek (was Lago) DataWheel {Brief}
6.1.4. ACL {None}
6.1.5. Cambridge On-Line Storage {Brief}
6.1.6. Spectra Logic {Brief}
6.1.7. Qualstar {Brief}
6.2. 3480
6.2.1. StorageTek {Brief}
6.2.2. EMASS (was GRAU) {Brief}
6.2.3. 3590 (Magstar,NTP) {Brief}
6.3. 4mm {Brief}
6.3.1. Cambridge On-Line storage {Brief}
6.3.2. Spectra Logic {Brief}
6.3.3. HP 4mm {Brief}
6.3.4. Storage Tek Datawheel {Brief}
6.3.5. Diverse Logistics Libra {Brief, New}
6.3.6. Qualstar {Brief, New}
6.3.7. ADIC {Brief, New}
6.4. VHS {Brief}
6.4.1. MountainGate (was Metrum)
6.5. Digital Linear Tape (DLT) (Quantum) {Brief}
6.5.1. TZ877 {Brief}
6.5.2. TL820 {Brief}
6.5.3. MountainGate
6.5.4. Breece Hill {Brief}
6.5.5. Odetics {Brief}
6.5.6. MediaLogic ADL
6.5.7. ADIC {Brief, New}
6.6. D-2
6.6.1. Ampex
6.6.2. Odetics
6.7. ID-1
6.7.1. Sony DMS, PetaSite {Brief}
6.8. Optical Disk (MO,WORM) Libraries
6.8.1. Hitachi 448 GB optical library
6.8.2. HP MO Autochangers
6.8.3. Maxoptix MO Autochangers
6.8.4. MountainGate {Brief}
6.8.5. DISC DocuStore {Brief}
6.8.6. Kodak {Brief}
6.8.7. Sony {Brief}
6.9. CD-ROM Jukeboxes
6.9.1. Pioneer
6.9.2. CyberTower {Brief, New}
6.9.3. NSMJukebox {Brief, New}
6.9.4. Nakamichi {Brief, New}
6.9.5. CDI Juke Box Library {Brief,New}
6.9.6. K & S M-200 {Brief, New}
6.9.7. DISC {Brief, New}
6.9.8. Meridian {Brief, New}

7. File Systems
7.1. NFS {Brief}
7.1.1. NFS V3
7.2. AFS {Brief}
7.3. DFS {Brief}
7.4. Log based file systems
7.5. Mainframe File Systems
7.6. Parallel System File Systems
7.7. Microsoft Windows NT {Brief}
7.8. Large Unix File Systems
7.9. Non-Unix Large File Systems

8. (Device) Interfaces
8.1. SCSI {Full}
8.1.1. Single ended vs differential
8.1.2. Asynchronous vs Synchronous Transfers
8.1.3. SCSI-I vs SCSI-II vs SCSI-III
8.1.4. Fast-Wide SCSI
8.1.5. Shared Busses / Performance {Brief}
8.1.6. Cabling/Hot Plugging {Brief}
8.1.7. Third Party Transfers/Separation of Control & Data Paths {Brief}
8.2. IDE {Brief}
8.3. IPI {None}
8.4. HIPPI {Brief}
8.4.1. HIPPI-6400 {Brief}
8.5. Ultranet {Brief}
8.6. Ethernet {Brief}
8.7. FDDI {None}
8.8. Fibre Channel Standard (FCS)
8.9. ESCONN/SBCON {Brief}
8.10. IEEE P1394 (Serial Bus)
8.11. Serial Storage Architecture (SSA)
8.12. S2I: IEEE P1285 Scalable Storage Interface
8.13. Multibus, Unibus, Mainframe Channels, and other history {None}

9. Other
9.1. Video vs Datagrade tapes {brief, 5/94}
9.2. Compression

10. Benchmarking

11. Mass Storage Conferences
11.0.1. THIC Tape Head Interface Committee {Brief, New}

12. MTBF (Mean Time Between Flareups, er, Failures)

13. Mass Storage Reports

14. Network-Attached Peripherals {Brief}

15. Other References
15.1. Print
15.2. Web
15.3. Newsgroups
15.4. Research Papers


17. Original Author's Disclaimer and Affiliation:

18. Copyright Notice

19. Additional Topics to be added
Subject: [1] Standards
From: Standards

There's a killer supply of computer-related standards at Fibre Channel and several
mass-storage-related items can be found there.

The ANSI and IEEE standards can be purchased in hardcopy form (the
only way some of them are available) from Global Engineering
Documents, (800)854-7179 or (303)792-2181.

Subject: [1.1] ANSI X3B5 {None}
From: Standards

Subject: [1.2] IEEE Mass Storage System Ref Model (OSSI) {Brief, 6/1/95}
From: Standards

The Storage Systems Standards Working Group now has a WWW page at

Version 5 of the model is available via as the files{1,2,3}.

The OSSI (Open Storage Systems Interconnection) Reference Model (its
new name) "provides the framework for a series of standards for
application and user interfaces to open storage systems." One of its
prime purposes is to define a common vocabulary. Claiming compliance
with the model at the moment has little practical value as far as
interoperation of different pieces from different vendors goes (which
is one of the ultimate aims of the still-distant standards that may
develop from this model).

Subject: [1.3] ECMA - European Computer Manufacturers Association {None}
From: Standards

Subject: [1.4] System Independent Data Format (SIDF)
From: Standards

This is a data format for tapes and removable disks, to facilitate
interchange between hardware and software platforms. See the FAQ at

Subject: [2] I/O Related Email Lists
From: I/O Related Email Lists

Here is a list of email reflectors for those who need to be deeply
involved in the technical details of various interfaces and standards.

April 6,
I/O Interface Related Reflectors (mailing lists)

Subscribe/ majordomo/
Reflector Unsubscribe Broadcast to listserv
Name Address Reflector keyword
------------- -------------------- ------------------------
SCSI scsi-request@symbios n/a (human)
ATA ata
ATAPI atapi
SSA ssa
IDETAPE idetape
Disk Attach disk_attach
10bit 10bit
CD-Recordable cdr
System Issues si
MultiMedia mmc
IEEE P1394 bob.snively@eng.1. n/a (human)
SFF bob.snively@eng.1. n/a (human)
IPI ipi-ext
HIPPI hippi-ext
Fibre Chan. fibre-channel-ext@think.
FC IP Prot. fc-ip-ext
PCMCIA pcmcia-gen
FC Class 4 majordomo@northyork. fc-class4
FC Isoch. majordomo@northyork. fc-i...@northyork.hp. fc-isoch com

All of the majordomo and listserv reflectors are automatic. To
subscribe or unsubscribe, send a message to the subscribe/unsubscribe
address with a line in the message body (not the subject line) of the
following format:

command reflector_name [your_email_address]

NOTE: At least for the reflectors at, your email
address is optional. If you include it and it doesn't match the
address in the email headers, there will be a delay while humans
verify your email address.


subscribe ata
subscribe ssa
subscribe ssa
subscribe atapi
subscribe mmc
subscribe fibre-channel-ext
subscribe pcmcia-gen
unsubscribe ssa

The other reflectors are managed by humans who are a little less picky
about the request format, but not quite as prompt. Please include
your name, email address, phone, and fax numbers in the message body
for the human-managed reflectors.

(with permission from John Lohmeyer, 95/5/10)

Subject: [3] Hierarchical Storage Management
From: Hierarchical Storage Management

HSM systems transparently migrate files from disk to optical disk
and/or magnetic tape, usually robotically accessible. Then when files are
accessed by a user, they transparently move them back to disk.

Watch for maximum file size limitations, sometimes limited by the
size of the media used, sometimes by the server's OS, and sometimes

Some offer integrated backup. Some will manage multiple copies of
files for data reliability.

Some offer integrated migration from other systems (ie, file servers
and/or workstations) to the central location disks, then to the central
location robotics. This generally requires changes to the on-disk file
system format on the migration clients.

An item to watch for is that the file management may be exactly like
Unix -- that is, all files appear to be online, and once they're
deleted, they're gone forever, even though the data may still be on

All of the subsections here are Unix-compatible (in various flavors)
unless indicated otherwise.

Additional Information:

See also _DEC Professional_, February 1993, Page 40 and _Client/Server
Today_, Dec. '94, p. 60.

The System-Managed Storage Guide by Howard W. Miller, $225 for first
copy, $75 for additional copies for same company available from The
Information Technology Institute, 136 Orchard Street, Byfield,
Massachusetts, 01922-1605.


Thomas Woodrow did an evaluation of NAStore, FileServ, DMF and Unitree
in 1993. It can be obtained through
or the Proc. 3rd NASA Goddard Conference on Mass Storage Systems and
Technologies, Oct. 1993, pp. 187--216. Somewhat dated now but
excellent methodology for comparing HSMs.

Subject: [3.1] Unitree {Brief}
From: Hierarchical Storage Management

The uncle of UNIX HSMs. Developed primarily at Lawrence Livermore
National Laboratories. Commercialized by a company called DISCOS,
then sold to OpenVision. UniTree was sold to UniTree Software in
December, 1994. See

Many versions exist on different hardware platforms, including a
National Storage Lab (NSL) UniTree commercialized by IBM - Fed
Systems. It's also available on SGI, Convex, and Amdahl hardware, at

See also "Epoch vs Unitree" below

For Convex, try

Jim Wilson
Business Development
Data Management Applications
Convex Computer Corporation

For most other platforms, call Open Vision at (800)223-OPEN or

New info:

The latest release of UniTree, V1.9.1, has the following changes:
- Available directly from UniTree Software Inc.
- Support DEC, HP-UX, SGI, Sun
- GUI(Tcl/Tk) tools for installation and administration
- New name database structure
- Common Message Logger
- Parallel Migration and Staging
- Multiple Storage Hierarchy (Optical/Tape)
- FTP performance improvements (Read/Write 20MBs/16MBs)*
- NFS performance improvements (Read/Write 3.5MBs/2MBs)*
- Rule-based dynamic migration
- Support for new robots (e.g., STK 97xx)
- Support >2GB disk partitions on Sun
- 64K File Families
- Configurable media and drive types
- Departmental File Server Configuration
- Compatible with most backup software (Legato, CAM, SMArch)

Demo copy available for download from web site:

New resellers in Asia, Europe, Australia

* Measured on a dual cpu Sun Ultra3000 with 256MB and 10 disks
Francis Kim Phone: (510) 833-3460
Director of Sales and Marketing FAX: (510) 833-9345
Unitree Software, Inc. e-mail:
11875 Dublin Blvd. Suite A200E WWW:
Dublin, Ca. 94568

Subject: [3.1.1] Epoch vs Unitree
From: Hierarchical Storage Management

(Note: this evaluation is old, and should be taken with a
grain of salt. rdv, 3/96)

(6/93) We just bought both last year. We bought an Epoch I
with the 20 GB EO and 327 GB worm. We will be upgrading it to an
Epoch II soon. We also bought Unitree from Titan to run on a Silicon
Graphics server and hook up to the STK 3480 silo. We hope to add more
silos eventually.

Unitree is licensed based on storage capacity while Epoch is not.
There may be an exception to this - STK just began reselling Epoch as
the front end for their silos and I'm not sure how they handle

My office mate and I (I handle Epoch, he handles Unitree) have enjoyed
comparing the merits/demerits of each over the last year. Comparison
in our case is slightly slanted due to the fact that the Epoch has
optical disk while the Unitree system has 3480 tape - so some
observations have more to do with media advantages/disadvantages.


+ Allows large files - can span volumes
+ Allows you to enlarge the cache easily, allows very large
+- Unitree has replaced several UNIX utilities with their own
(FTP, NFS and the file system). This allows certain features to
work but is generally slower and disallows access to the archive when
you are on the server itself - unless you NFS mount!
+ Allows deleted files to be saved for a specified time
+ Allows multiple copies of files to be kept
+ Data is copied to archive soon after creation
+ Unitree runs on several different platforms
- Does not allow access to data until it is completely
- Behaves poorly with small files (due to necessary overhead)
- Unitree is licensed to several vendors, so versions differ
- NFS access is so slow that we recommend it not be used for
file transfer - only for ls and du, etc. Use FTP.
- The Silicon Graphics version is still new and has some


+ Allows access to the data as soon as part of it is loaded
+ Company seems serious about reputation and support
+ The Epoch II is based on a SUN system, with few
+ Data is copied to archive only when the cache space is
+ All native UNIX transfer methods work - NFS, FTP and RCP
+ Add on products greatly simplify backup and extend
archiving features to other systems.
- Deleted files are gone forever
- Currently only available on SUN. This will change.
- Cannot span volumes yet - limiting file size
- Has the SUN limitation of 2 Gb per filesystem. This would
be a bigger problem if you used it for a 3480 silo.
{Note 2GB of Magnetic Disk limit, not the entire HSM store}
- Behaves poorly with small files (due to necessary overhead)
- Since inodes are kept on magnetic cache, you must take
into account the maximum number of files you will ever need.
- Since inodes are always on disk, certain disk operations
can take forever since all inodes must be examined.
- Enlarging a magnetic disk filesystem which has associated
archive media requires you to offload all data and then reload it.
If anyone has found another way, I would like to hear about
{Others did offer some easier work-arounds}

In all fairness to Titan, they have been addressing any problems and
it has been improving. Epoch too plans to address some of their
shortcomings. We are looking forward to growing with both products.

The likelihood that the various flavors of Unitree will standardize
depends on what happens with Discos. My guess is that some
features/enhancements will be filtered back to the base product
released by Discos. Bye...

(,, Tom Bodoh, USGS/EROS Data
Center, Sioux Falls, SD)

Subject: [3.2] National Storage Lab {Brief}
From: Hierarchical Storage Management

NSL is an industry consortium (American companies only) that has a
version of Unitree, and is creating their own new High Performance
Storage System.

HPSS, among other features, supports striping of removable media, and
full 64-bit files. Some of the work is being done at LLNL, where
UniTree was originally developed.
There's a good overview reachable at


Subject: [3.3] HIARC {New}
From: Hierarchical Storage Management

HIARC HSM runs on Solaris 2.4 and above. Slides in at the vnode
layer. Supports 4mm, 8mm, 3480, DLT, VHS, D-1 and D-2 tape drives,
and appropriate robotics (I don't have a specific list). Removable
media formats are standard (_which_ standard, I don't know). Pricing
from $4k to $25k is reasonable for the functionality. See (rdv, 97/3/20)

Subject: [3.4] Epoch (also known as StorageTek's NearNet) {Brief}
From: Hierarchical Storage Management
See also "Epoch vs Unitree" in Appendix

Subject: [3.5] Zetaco/NETstor {Brief}
From: Hierarchical Storage Management

NETstor can be reached at

NETstor, Inc. (formerly Zetaco, Inc.) is a leading provider of
hierarchical online mass-storage systems for open systems. Primarily
NFS accessable systems with magnetic disks and optical-disk libraries.
They have marketing agreements with Digital Equipment Corp, and


Netstor was bought by Cheyenne, and is now sold by them
(, 10/95).

Subject: [3.6] R-Squared Infinity IFS 2 {Brief}
From: Hierarchical Storage Management

Contact: Steve Wine, Manager, Mass Storage Products, R-Squared, 11211
East Arapahoe Rd, Englewood, CO 80112, 303/799-9292 or FAX 303/799-9297

Subject: [3.7] AMASS
From: Hierarchical Storage Management

From Advanced Archival Products. Supports a huge range of devices,
autochangers, and operating systems. Block-based movement of data
between the hard disk cache and tape or optical tertiary storage.
Systems run from a few gigabytes up to at least 12 TB, with prices
dependent on capacity. New versions allow multiple cache disks. Slips
right in to the VFS layer and looks like a normal Unix file system,
with the plusses and minuses that entails. No file versioning or
multiple copies yet. File creation is an Achilles' heel on
performance. Since it's block based, files can be larger than a piece
of media. Separate product DataMgr will migrate files from client
machines to the AMASS server automatically (with FS changes, of

AMASS is now owned by EMASS, and you can find info at
(rdv, 1996/3/27)

Subject: [3.8] Tracer XFS {None}
From: Hierarchical Storage Management

Subject: [3.9] Metior
From: Hierarchical Storage Management

Metior (pronounced like meteor) is targetting an incredibly broad
market, from laptops with removable media through supercomputers, with
prices from $650(!) to $118K. They handle multiple coordinated copies,
so off-site backup can be automatic. Can do migration for client
machines (with appropriate software licenses and changes to the file
system). The hierarchy seems to be extremely flexible, variable on a
per-user or per-group basis. Machines without client licenses can
mount the Metior FS using NFS. Runs on Suns, SGI, and HP 9000/700. ANT
is new, and they've only got a handful of customers so far, but it
looks _very_ interesting.

(info from, written by rdv, so it's my fault if it's
not accurate) (rdv,94/7/7)

More information available on the WWW FAQ version.
Also see them at

Automated Network Technologies
3333 South Bannock Street, Suite 945
Englewood, CO 80110 USA
Phone 303.789.2506
FAX 303.789.2438

Subject: [3.10] NAStore {Brief}
From: Hierarchical Storage Management

NAStore is a Unix migrating file system developed by the Numerical
Aerodynamic Simulation program at NASA Ames. It is available through
NASA's software distribution agency, COSMIC. It currently runs only on
Convex with 34x0 cartridges and Storage Tek robots. Looks like a local
file system to users of the Convex. Available with source.

Info on NAStore can be found on the web at

COSMIC's address is :
University of Georgia
382 East Broad Street
Athens, Georgia, 30602-4272, US

For more information on NAStore, contact John Lekashman,
(info from Bill Ross,, 94/9/15)

Subject: [3.11] DMF {Brief}
From: Hierarchical Storage Management

Cray Research's Data Migration Facility. The grandaddy of Unix HSM
systems. You can find info on DMF at, or call +1 612
683 3897 or email It's reportedly
running on more than 200 systems, and development is continuing. Large
users are in the hundreds of TB, with millions of files and >1TB/day
through DMF.

Information from:
"Storage Management at Cray Research, Inc", Metcalfe, D.J. and Thompson. D.
"Data Migration Facility Development Update", Lazatella, T.W. and Bannister, N.
Cray User Group, Barcelona, 1996, in press.

(, 1996/4/2)

Subject: [3.12] FileServ {Brief}
From: Hierarchical Storage Management

From E-Systems. Works with the E-Systems ER-90 (D-2) tape drive and
Odetics robots, as well as 3480 with the Storage Tek ACS 4400. Runs on
Convexes (only?). Supports multiple copies of files. Retrieves only
necessary info from tape to disk before completing request.

Reportedly no longer available on Convex, in beta test on SGI
(, 10/95)

Now owned by EMASS, info at

Subject: [3.13] Cray Research's Open Storage Manager {Brief}
From: Hierarchical Storage Management

They have some agreement with Legent Corporation. OSM runs on Sparc
machines, including the Cray Superservers. Price ranges from $500 to
$5,000, which is very cheap for HSM. However, it might only be capable
of migrating among disks -- I don't see any mention of autochangers.
(rdv, 94/12/9)

Subject: [3.14] T-mass {None}
From: Hierarchical Storage Management

Subject: [3.15] HP OpenView OmniStorage
From: Hierarchical Storage Management

Supports multiple types of tertiary media (optical, tape) though it
seems to come originally from their work for their own MO jukeboxes.
Supports multiple types of clients. (info from Herbert Volk
<>, 1995/9/28)

More info available at Now a very broad
storage management suite, covering lots of functionality for
management. Supports MO, DLT and 8mm as media, though only a limited
number of autochangers. (rdv, 98/1/16)

Subject: [3.16] Platinum NetArchive-HSM {Brief, New}
From: Hierarchical Storage Management

Used to be ASC (Advanced Systems Concept) before being bought by
Platinum. Runs on SunOS, HP, and Domain/OS. Supports numerous optical
jukeboxes. See (rdv, 96/4)

PLATINUM technology, inc.
1815 South Meyers Road
Oakbrook Terrace, IL 60181
1-800-442-6861 -or- 708/620-5000

Subject: [3.17] Large Storage Configurations {Brief,New}
From: Hierarchical Storage Management describes their Solaris-based HSM product. Only one
computing platform, but a reasonably broad range of mid- to high-end
peripherals and robotics supported, from little Exabyte autochangers
to the IBM 3494 and STK silos. (rdv, 96/7/23)

Subject: [3.18] Unix HSM Vendor List
From: Hierarchical Storage Management

This list is adapted from _Client/Server Today_, Dec. '94, with some
of my own additions. All the phone numbers are USA (apologies to
international readers for the 800 numbers, but they're all I've got).
I don't know anything about some of these companies; I suspect some of
them work with HSM from other vendors rather than their own packages.

I've indicated on the list various reports of companies OEMing from
each other; this is not out of disrespect for the work involved in
OEMing/supporting or porting such complex software, but an attempt to
divide the HSM vendors into "families" with similar capabilities
(occassionally on very disparate platforms).

Vendor Product Contact
------ ------- -------
Advanced Archival Products AMASS (303)792-9700 *
Advanced Software Concepts (ASC) (619)737-9544
Alphatronix ASC (919)544-0001
Artecon ASC (619)931-5500
AT&T CommVault DataMigrator (908)935-8000
Automated Network Technologies (ANT) Metior (303)789-2506 *
Computer Associates International (800)225-5244
Computer Upgrade (808)874-8807
Convex Computer UniTree (214)497-3085 *
COSMIC (NAStore) (706)542-3265 +
Cray Research DMF (800)BUY-CRAY *
Digital Equipment (DEC) NETstor (800)344-4825
Dorotech (703)478-2260
Epoch Systems (508)836-4300 *
E-Systems FileServ ?*
File Tek Storage Machine (301)251-0600
Fujitsu Computer Products of America OSM (408)432-6333
Hewlett-Packard OmniStorage* ,NETstor (800)637-7740x8509
HIARC (714)253-6990
IBM UniTree (800)225-5426
Introl (612)788-9391
Large Software Configurations (LSC) (612)482-4535 *
Legent $OSM (703)708-3000
National Storage Lab (NSL) HPSS +*
NETstor (Cheyenne) $NETstor (612)890-9367
(OpenVision UniTree (510)426-6400 *)
Platinum NetArchive HSM (708)620-5000 *
Qstar Technologies (301)762-9800
Raxco (301)258-2620
Software Partners/32 (508)887-6409
Storage Technology (STK, StorageTek) (303)673-5151
T-mass ?
Tracer XFS ?
UniTree Software UniTree (510)833-9344 *

* = Info elsewhere in FAQ
+ = not commercial product
? = no contact info
$ = original developer (no mark indicates OEM)

Subject: [3.19] Mainframe
From: Hierarchical Storage Management

IBM also has HSM for MVS, called, imaginatively, HSM.

There is the storage home page. I
have also found references to System Managed Storage SMS and HSM and
DFHSM (Data Facility Hierarchical Storage Manager) but could find no
online information. There are probably manuals like DFHSM Version 2
Release 5.0, General Information manual (GH35-0092) if you are a real
glutton for punishment and have a friend at ibm.

So we have ADSM and DFHSM and DFSMS and probably others. But not much
online information. Sorry.

A little searching from the might turn up something

(Del Cecchi, <dce...@VNET.IBM.COM>, 1996/3/27)

Subject: [3.20] PC & PC Server Oriented Packages
From: Hierarchical Storage Management

Subject: [3.20.1] HP Optical Jukebox Storage Solution
From: Hierarchical Storage Management
Netware 3.11 based, up to 10.4 Gigabytes, includes model 10LC optical
jukebox which has one drive and 16 disks each with 650 MB formatted capacity.
Hewlet-packard (Palo Alto, CA) 800/826-4111.

Subject: [3.20.2] Chili Pepper Software
From: Hierarchical Storage Management

A company from Atlanta, GA named Chili Pepper Software (404-339-1812)
and 3M have gotten together in some fashion to make HSM software for
PCs using QIC. (rdv, 94/9/5)

Subject: [3.20.3] Cheyenne ARCserve
From: Hierarchical Storage Management

Runs on Netware servers. Transparent to most clients, but has a neat
feature: if you use a special TSR and DLL on client PCs, when it has
to retrieve a file from secondary or tertiary storage, it can give you
an estimated retrieval time and the option to abort. (516)484-5110,

Subject: [3.21] DATMAN {Brief}
From: Hierarchical Storage Management

Simple HSM for 4mm tape drives under MS-DOS. A limited freeware
version is available.

More info at
Voice: 708-369-7112 Fax: 708-369-7113 (Kan Yabumoto,, Nov. 1995)

Subject: [3.22] Windows NT
From: Hierarchical Storage Management


Avail Systems
4760 Walnut St
Boulder, CO 80301
voice: +1.303.444.4018
fax: +1.303.546.4219 (Dave Skinner) (95/2/12)

Avail's product, NetSpace HSM, has been selected by Microsoft to be
incorporated into future versions of NT, and also provides a link
between NetWare and IBM's ADSM. NetSpace also runs on Novell NetWare
systems. See ("Wight, Risa" <>,

Subject: [3.23] Other Non-Unix HSM
From: Hierarchical Storage Management

DEC's old Tops-20 OS supported offline files, and would generate an
automatic request to the operator to mount a tape when the user
accessed the file. When you listed a directory, it would show you
which files were online and which off.

DEC's OpenVMS has some sort of support for this now. VMS 6.1 supports
"shelved" files.

There is also the product Virtual Branches, from Acorn Software, which
does HSM for MO and CD-ROM for OpenVMS.

Acorn Software, Inc.
267 Cox St.
Hudson, MA 01749
voice: (508)568-1618
fax: (508)562-1133

Subject: [3.24] Tapes as Disks {Brief, New}
From: Hierarchical Storage Management

There are several packages around (mostly for PCs) that will let you
use a tape drive like a disk drive. Of course, it's _very_ slow
unless it uses some disk-based information as well.

See for one such product. (rdv, 96/11/4)

Subject: [4] Backup Software
From: Backup Software

Backup software usually provides some form of management of files,
tapes, and autochangers. Retrieval of files is not automatic (as in
true HSM). These are designed to allow you to recover from disk or
file system failures, and to recover files accidentally (or
maliciously) deleted or corrupted. Some work in conjunction with HSM
systems, which are often vulnerable to the latter class of problems.

I've concentrated here on backup software that supports various
autochangers, as this is of more interest to people in this group than
standalone software for backing up one hard disk onto one tape.

Subject: [4.1] PC-Oriented Backup Packages
From: Backup Software

I don't think any of the PC operating systems come with tape support
built in, so you have to have some 3rd party software to work with
tape. This short list is primarily oriented toward PC servers.
It's partly derived from _PC Magazine_, March 29, 1994, pp. 227-272.

Note that there has been an ongoing discussion of the pitfalls of
Windows 95 and third-party backup software; many in particular are
having trouble with long file names.

Arcada Software - Storage Exec. (NT)
Avail (NT)
Cheyenne Software - ArcServe (Netware)
Conner Storage Systems - Backup Exec (Netware)
Emerald Systems - Xpress Librarian
Fortunet - NSure NLM/AllNet
Hewlett Packard - OmniBack II (NT)
Legato - NetWorker (Netware)
Mountain Network Solutions - FileSafe
NovaStor (Netware)
Palindrome - Network Archivist (Netware, OS/2, Windows)
Palindrome -Backup Director
Performance Technology - PowerSave (Netware)
Systems Enhancement - Total Network Recall

Arcada is at 800/327-2232 and at

{Under Construction}(SHMO)

Subject: [4.2] Unix Packages
From: Backup Software

Some people claim "Unix tape support is an oxymoron," so there's a big
market in outdoing tar, dump, dd and cpio.

APUnix - FarTool
Cheyenne - ArcServe (see under PCs, above)
Dallastone - D-Tools
Delta MicroSystems (PDC) - BudTool
Epoch Systems - Enterprise Backup
IBM - ADSM (Adstar Distributed Storage Manager)
Hewlett Packard - OmniBack II
Legato - Networker
Network Imaging Systems
Open Vision - AXXion Netbackup 2.0 Software
Software Moguls - SM-arch
Spectra Logic - Alexandria
Workstation Solutions

{Under Construction}(SHMO)

Subject: [4.2.1] Spectra Logic Alexandria
From: Backup Software

Spectra Logic makes 4mm & 8mm autochangers, but this software supports
other autochangers as well. Has a nice feature that it claims to be
capable of backing up live Oracle, Informix and Sybase databases.
email (rdv,95/2/14) On the web at

Subject: [4.2.2] ADSTAR Distributed Storage Manager
From: Backup Software

Runs on everything from OS/2, AIX and OS/400 to VSE/ESA, MVS and VM
providing backups for virtually everything you can think of in PCs and
workstations. (800)IBM-3333 or anonymous ftp to

Subject: [4.2.3] NetWorker
From: Backup Software

Backup software. See Runs on a wide variety of
platforms and supports a bunch of types of autochangers.

Legato Systems, Inc.
3145 Porter Drive
Palo Alto, CA 94304
Phone: 415-812-6000
Fax Number: 415-812-6032
Fax-on-demand: 415-812-6156

Subject: [4.2.4] BudTool {Brief}
From: Backup Software

PDC Engineering
111 Lindbergh Avenue
Suite C
Livermore, CA 94550 USA
(510) 449-6881
FAX (510) 449-6885


Subject: [4.2.5] HP OmniBack II {Brief, New}
From: Backup Software

HP's OmniBack II runs on several different platforms, and splits the
functionality up. The Backup manager appears to run only on NT, but
it can use devices attached to various flavors of Unix, and backs up
ten different kinds of Unix and PC clients. Now marketed jointly with
OmniStorage, their HSM system, in a (sales) program they call
OpenView. See (rdv, 98/1/16)

Subject: [4.2.6] Workstation Solutions {Brief}
From: Backup Software

See Runs on a variety of Unix platforms, and
supports a reasonably broad range (20GB-5TB) of autochangers and tape
systems (4mm, 8mm, DLT, VHS). (rdv, 96/7/8)

Subject: [4.2.7] Amanda {Brief, New}
From: Backup Software

Subscribe to and for some time. The "current"
distibution of Amanda seems to be from,
with version A very good backup system, with no dollar
investment. (David Olsen, <>, 1/23/97)

You'll also find a FAQ on it at

Subject: [4.2.8] Remote Backup or Mirroring {Brief, New}
From: Backup Software

It's now possible, in several fashions, to backup systems over a
network or even a modem, for recovery from fires and even disk

Channel extenders, such as the CHANNELink from CNT and the Symmetrix
Remote Data Facility, are used by some
mainframe systems to create remote copies of disks (remote mirroring)
as a disaster recovery measure. Early systems used dedicated fibre or
telephone lines and ran proprietary communications protocols. Newer
systems from CNT are capable of communicating over general-purpose
wide-area networks, thus saving the costs of the dedicated lines.

It's also possible to backup PCs over your modem in an incremental
fashion, through your ISP; one example is

Two other companies that do this over the Internet (out of, I believe,
more than 30) are Connected Corp., Framingham, MA; Virtual Technology
Corp., Minneapolis, MN.

Subject: [5] Tape and Autochanger Management Software
From: Tape and Autochanger Management Software

This category of software can overlap with both HSM and backup, above,
and basic tools are often available from the autochanger hardware
vendors, below. New additions to this category welcome -- I'm sure
there are numerous vendors I don't know. Functionality varies widely,
from rudimentary "move the cartridge" interfaces to sophisticated
tape-tracking databases. (rdv, 95/6/1)

Subject: [5.1] REELlibrarian
From: Tape and Autochanger Management Software

Actually a whole set of software tools from Storage Tek, available
through Software Clearing House,
Manages different types of media for you, including 3480 in STK silos,
under MVS or Unix. (rdv from, 95/6/1)

Subject: [5.2] ANT Medium Changer
From: Tape and Autochanger Management Software

There is a public version of a Solaris 2.x Medium Changer driver
with a set of command line utilities in our FTP server.
Only restriction is that you cannot bundle it with another product
or resell it (intended for end-user use only).
or (Tim Sesow, ANT, 1995/9/21)

Subject: [5.3] Tapes 3000 {Brief}
From: Tape and Autochanger Management Software

Tapes3000 is a UNISON/TYMLABS product that puts a label on a reel
tape, DDS, any kind of media storage and adds it to a "tapes database"
so you do not have to manually log and label backup tapes or special
request tapes, and possibally make a mistake. You can also use this
for unlabeled media, but then you would have to manually log the
media. You are able to set a "dataset" for differrent retentions
(Generations, weekly, monthly, daily etc). Then when those criteria
are met the program will automatically scratch those tapes, then you
run a report and it will give you a list of what scratched for that
day, week, or whatever time you want to run the job.

Tapes3000 is part of a package that you can receive called MAESTRO
which is a job scheduler program. Not an autochanger control package,
just tape management software. (R Johnson
<>, 1996/3/25)

Subject: [5.4] Others
From: Tape and Autochanger Management Software

Many of the HSM (including EMASS, above, with their VolServ) and
backup vendors also sell simple autochanger control interfaces. Check
with them.

Some things I've read indicate that one or more of the
university-based projects ought to have a freely available autochanger
controller; if anybody has any info on this let me know.

Subject: [6] Robotics (Autochangers, Jukeboxes, Stackers, Libraries)
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

I use the term "robotics" to refer to access to multiple removable
volumes by a fewer number of drives without a person. This includes
sequential stackers, as well as random access robotics.

A stacker typically is capable of taking (literally) a stack of tapes
and putting them into the drive one at a time, in order. No random
access to specific tapes, as with a full-function autochanger.
Stackers typically are limited to 8-10 cartridges, and are used by
people whose backups have exceeded the size of one cartridge.

In the larger media formats, such as D-1, D-2, Betacam, etc., the
traditional manufacturers of broadcast autochangers, such as Asaca,
Odetics, Sony, etc. have products that are easily adaptable to storage

The August 1996 issue of Byte magazine has an article comparing 12
tape autochangers. It is a little misleading, not mentioning any of
the truly large library systems, and only one midrange, whose capacity
is quoted assuming DLT 7000 tape drives, which is never mentioned. In
addition, much of their testing is more related to the drives than the

Subject: [6.1] 8mm {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Subject: [6.1.1] Exabyte {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Phone: 800/EXABYTE, 1685 38th st, Boulder, CO 80301, Fax 303/447-7689.
On the web at

Subject: [] EXB-10h
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Current model, 10 cartridges, one drive. Not Mammoth compatible. 70
GB, uncompressed. (rdv,96/8/29).

Subject: [] EXB-210
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

2 drives, 11 cartridges, not Mammoth compatible.

Subject: [] EXB-220
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

2 drives, 20 cartridges, Mammoth compatible (rdv,96/8/29).

Subject: [] EXB-440/480
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

40 or 80 cartridges, 2 or 4 drives, Mammoth compatible. 1.6 TB
uncompressed, with Mammoth. (rdv,96/8/29).

Subject: [] EXB-10
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Ten cartridges, one full-height drive. Original 10 cartridge robot.
No robotic intelligence, when one tape comes out, the robot mounts the
next tape in sequence (i.e. a kind of stacker). Button selectable to
loop back to the first tape or to stop at the end. Discontinued.

Subject: [] EXB-10i
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Ten cartridges, one full-height drive. Released
shortly after the EXB-10. Includes SCSI attachment to robotics. Now
nearly replaced by the EXB-10e. Discontinued.

Subject: [] EXB-10e
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Ten cartridges, one full-height drive. Announced around 4/93.
Includes better control panel and display than EXB-10i. Drive mounted
horizontal and tape magazine at slight angle (rather than vice-versa
in EXB-10i). Discontinued.

Subject: [] EXB-120
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Holds 120 8mm cartridges, up to four full-height drives.

Subject: [6.1.2] ADIC {Brief, New}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

I'm not sure if ADIC manufactures or OEMs their robotics, but they
apparently sell to end users. They have 8mm, 4mm and DLT autochangers
in a variety of small to medium sizes, up to about a terabyte. See (rdv,97/3/18)

Subject: [6.1.3] Storage Tek (was Lago) DataWheel {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Holds 54 8mm tape cartridge in a carousel with 2 8mm drives. The
carousels are removable. Now Storage Tek, used to be a small company
called LAGO, which apparently no longer exists.

You'll find info at: (rdv,
updated 1996/3/22)

Subject: [6.1.4] ACL {None}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Subject: [6.1.5] Cambridge On-Line Storage {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)
Sixty and 240 GB libraries, 713/981-3812

Subject: [6.1.6] Spectra Logic {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Spectra Logic makes SCSI-controlled 8mm and 4mm (DAT) autochangers.
One to four drives, with 20 to 60 slots. Capacity currently up to 600
GB of DDS-2 (4mm) or 300 GB 8mm. Early models (STL-6000 & STL-8000)
were a rotating carousel. Newer ones use an arm and the tapes don't

Supported by a variety of software vendors. List prices of $9K
(Spectra 4000/20 slots, one DDS-2 drive) to $31K (60 slots with four
drives and barcode support) including drives.

They also make a thing called TapeFrame, which consists of several of
their autochangers working in conjunction, with capacities up to 2.2

U.S.: 1-800-833-1132 or 303-449-6400

(Britt Terry,, 95/1/12)

See also under backup software, and on the web at

Subject: [6.1.7] Qualstar {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Makes 8mm libraries that hold 10 to 120 cartridges and 2 to 6 drives.
tel:(818)592-0116 fax:(818)592-0061 or

Our TLS-4000 8mm library family now supports the Sony SDX-300C drive.
Production shipments have started and enduser installations have
occurred. Early field reports are completely positive.

TLS-4000 also supports Exabyte Mammoth and 8505XL drives.

(Bob Covey,, 96/10/22)

Subject: [6.2] 3480
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Subject: [6.2.1] StorageTek {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Storage Tek makes huge autochangers, referred to as silos, round and
several (~5) meters in diameter. They hold 6,000 3480-style tapes. At
original 3480 densities, that's only 1.2 TB per silo, but capacities
have gone up to (I think) 800 MB/cartridge, and are poised for a HUGE
jump if Storage Tek gets their Redwood tape drive finished (in beta
test, 12/94), up to 20 GB/cartridge, 120 TB/silo.

There is a smaller silo, known as WolfCreek, that holds 500-1000

STK also OEMs a 3480 autochanger from Odetics. Holds ~260 cartridges,
I think, in rotating drum, with room for ?2? tape drives above it.
(rdv,95/1/12) However, I couldn't find any info about this on the web

They also have a web site at (95/5/16,rdv)

All but the Odetics (known as Ocean, I think) are Redwood-compatible.

The new 9710 (codenamed Panther) can handle both DLT and 3480
cartridges in a mini-tower. (, 1996/3/12)

Subject: [6.2.2] EMASS (was GRAU) {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Grau, a German manufacturer, makes high-end, very large capacity
mixed-media autochangers known as the ABBA series, targetted I believe
primarily at the IBM mainframe market. (rdv,94/11/7)

Bought by EMASS, see They support 3480, D-2, MO,
VHS, DLT, 8mm all in one robot, so they renamed the autochanger series
the AML, Automated Mixed-Media Libraries.

Subject: [6.2.3] 3590 (Magstar,NTP) {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

MountainGate has announced that they will have, later this year, a
300-cartridge autochanger.

IBM of course makes numerous autochangers for NTP; the 3494 and 3495
models both support it. More info at (They probably
have smaller libraries, too.)

Word in the newsgroup has it that STK robots won't support Magstar due
to the rivalry between IBM and STK.


Subject: [6.3] 4mm {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Subject: [6.3.1] Cambridge On-Line storage {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)
Libraries of 120 and 40 GB, 713/981-3812

Subject: [6.3.2] Spectra Logic {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Spectra Logic makes SCSI-controlled 8mm and 4mm autochangers. See
above under 8mm autochangers.

Subject: [6.3.3] HP 4mm {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

I think HP makes their own 4mm autochangers.

Subject: [6.3.4] Storage Tek Datawheel {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

The 4mm version. 25 cartridges, so up to 100GB uncompressed. Info at

Subject: [6.3.5] Diverse Logistics Libra {Brief, New}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Two libraries, the Libra-8 and Libra-16, with 8 or 16 slots (32 or 64
GB uncompressed) and one DAT drive. Info at or (Europe), or ( (Marc SCHAEFER), 96/8/6)

Subject: [6.3.6] Qualstar {Brief, New}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)


We are now shipping our TLS-2000 4mm tape library family. This product
line consists of 6 models ranging from 1-2 drives with 18 tapes, to 1-4
drives with 144 tapes. All units include a mailbox and barcode support. I
believe that the TLS-24144 is the largest 4mm library in production.
TLS-2000 supports Seagate, Sony and HP DDS-2 drives and we are about to
start testing the Sony SDT-9000 DDS-3 drive.
(Bob Covey,, 96/10/22)

Subject: [6.3.7] ADIC {Brief, New}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

I'm not sure if ADIC manufactures or OEMs their robotics, but they
apparently sell to end users. They have 8mm, 4mm and DLT autochangers
in a variety of small to medium sizes, up to about a terabyte. See (rdv,97/3/18)

Subject: [6.4] VHS {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Subject: [6.4.1] MountainGate (was Metrum)
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Metrum's data storage division was bought by Lockheed Martin and
renamed MountainGate.

Autochangers for their VHS-based high-capacity (20GB, 2 MB/sec.) tape
drive. They now have a stacker available for standalone drives.

Library of 960 GB (RSS-48b) holds 2 drives and 48 cartridges in a
rotating drum.

Library of 12 TB (RSS-600b) holds 5 drives and 600 cartridges in less
than 20 square feet of floor space. The tapes are held in rotating
drums on each side, with the drives in a rack in between.

OEMs through Convex, IBM, and a host of resellers. Integrated with
various backup and HSM packages, including UniTree from Convex & IBM,
and AMASS from AAP.

See MountainGate also under MO and DLT autochangers.

A Lockheed Martin Company
9393 Gateway Drive
Reno NV
702-851-9393 Phone
702-851-5533 Fax

See them on the web at, but as of today
(1996/3/19) doesn't have much on the high-end products.

Subject: [6.5] Digital Linear Tape (DLT) (Quantum) {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

T* names are DEC's names, DLT2* names are OEM names.

Subject: [6.5.1] TZ877 {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

One TZ87 tape drive, 7 cartridges, each 10GB native
Presumed to be the same as the DLT2700 library.

Ref: Digital's Customer Update, March 14, 1994

Subject: [6.5.2] TL820 {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Holds 3 TZ87 tape drives, 264 catridges, five libraries attachable
Presumed to be Odetics made (714/774-5000)
About $150K U.S.

Ref: Digital's Customer Update, March 14, 1994

Subject: [6.5.3] MountainGate
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

At Comdex '94 in Vegas, Metrum (now MountainGate) introduced the D-900
(900 cartridges, up to 20 drives, 9TB uncompressed for DLT-2000) and
D-360 (360 cartridges, up to 8 drives, 3.6 TB uncompressed for
DLT-2000) DLT autochangers. There is an expansion unit with 480
cartridges which may hold two drives. Up to eight D-360 or D-480 units
can be connected via passthrough. They also introduced 28 and 60
cartridge DLT autochangers. Customer shipments starting in early '95.

See above under VHS for contact info.

Subject: [6.5.4] Breece Hill {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Breece Hill makes two small (28 and 60 cartridges) DLT autochangers.
On the web at

Breece Hill Technologies, Inc.
6287 Arapahoe Avenue
Boulder, Colorado 80303 USA

For more Information 1-800-941-0550 or 303-449-2673

Subject: [6.5.5] Odetics {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Odetics makes a series of DLT libraries that hold, in the basic
configuration, 3 DLT drives and 264 cartridges. See

Subject: [6.5.6] MediaLogic ADL
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

MediaLogic ADL, Inc.
1965 57th Court
Boulder, CO 80301
Voice: 303-939-9780
Fax: 303-939-9745

They have desktop autochangers up to 26 DLT cartridges. See also on the web. Also have 4mm and 8mm
autochangers that are similar. I don't know if they manufacturer these
or OEM them. (rdv, 1996/3/19)

Subject: [6.5.7] ADIC {Brief, New}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

I'm not sure if ADIC manufactures or OEMs their robotics, but they
apparently sell to end users. They have 8mm, 4mm and DLT autochangers
in a variety of small to medium sizes, up to about a terabyte. See (rdv,97/3/18)

Subject: [6.6] D-2
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Subject: [6.6.1] Ampex
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)
Ampex makes their own autochangers for the DST DD-2 tape drive (see
part 1 of the FAQ).

DST 410 Automated Cartridge Library:
Up to 1.2 terabytes capacity (uncompressed) in 7 square feet of floor space.

All 3 cartridge (cassette) sizes supported - 25, 75, 165 gigabytes

SCSI Medium Changer Commands or Ethernet NetSCSI protocol.
Console mounted configuration.
Single unit price: $150K.

DST 810 Automated Cartridge Library:
Up to 6.4 terabytes (uncompressed) in 21 square feet of floor space.
Robotic performance of 600 cartridge exchanges per hour.
Average access time to any file less than 30 sec. (including cartridge
exchange, drive load and search to data).
1 to 4 tape drives per library.
Ethernet NetSCSI protocol robotics control.
Starting single unit price: $300K.

(, 94/12/23)

Subject: [6.6.2] Odetics
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Odetics makes a thing called a DataTower that holds ~250 S-size D-2
cartridges. It used to be, but is no longer, sold through EMASS for
use with the ER-90 (the Ampex/EMASS D-2 drive). It's a small silo that
sits in front of one rack of drives.

They also make an expandable library known as the DataLibrary, with a
maximum capacity of ten petabytes(!) (ten million gigabytes). A robot
handler runs on a track down an aisle lined with cartridges, and tape
drives at one (both?) end(s) of the aisle. I think the aisles can vary
in length, and they can be lined up next to each other and I believe
cartridges will pass between them.

(Note: since their acquisition of GRAU (above) EMASS no longer sells
Odetics. I don't know if these are still available directly from
Odetics and who you'd get to do the integration work. (rdv, from (Dave Barnes), 1996/3/22))

Subject: [6.7] ID-1
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Subject: [6.7.1] Sony DMS, PetaSite {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Sony sells three autochangers for their ID-1 line of tape drives,
based on their broadcast line of autochangers. These are known as the
DMS Series, models 24, 300M, and 700M. Not surprisingly, they hold,
respectively, 24 (S,M, or L cassettes), 300 (M only) and 700 (M only)
cassettes for capacities of 2.3, 13, and 30 terabytes.

They have also announced something called PetaSite, which they claim
expands to 3 petabytes and supports both ID-1 and DTF in a single

(rdv, 1996/3/22)

Subject: [6.8] Optical Disk (MO,WORM) Libraries
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Several other Japanese manufacturers make optical libraries, I think,
mostly in support of their own drives. (SHMO)

Subject: [6.8.1] Hitachi 448 GB optical library
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)
12-inch worm, up to 7GB per platter, 2-4 drives, additional cartridge
expansion unit increases capacity 560 GB to 1,008 GB.
Drive rates up to 2.22 MB/sec.
Phone: 800/HITACHI

Subject: [6.8.2] HP MO Autochangers
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Makes several models, from 16 disks and one drive up to 144 disks and
?4? drives. These are very popular.

Subject: [6.8.3] Maxoptix MO Autochangers
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Makes several models in the MaxLyb series, the 52, 120 and 180, which
correspond to the capacity in gigabytes for 1.3 GB drives. They hold,
respectively, 2 (52), 2 or 4 (120) and 2, 4 or 6 (180) drives.

They also have a fairly mysterious thing called the Axxis^26, a "high
speed network file retrieval & backup server," which is obviously an
MO autochanger, apparently bundled with a license for Palindrome
Backup Director, suitable for attaching to your Netware file server?

tel: (408)954-9700, (800)848-3092
fax: (408)954-9711


Subject: [6.8.4] MountainGate {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Now has the OSS-626, which holds 450-626 disks and 2-24 full-height HP
drives. Also a new expandable multi-chassis autochanger similar to the
D-360 DLT autochanger is available.

See above under VHS for contact info.

Subject: [6.8.5] DISC DocuStore {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Makes large libraries (up to ~1,000 5.25" MO catridges, 2.6TB for
standard MO or 4.6TB for non-standard); see (Stephen Fister <fis...@Synopsys.COM>, 96/8/7)

Subject: [6.8.6] Kodak {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Kodak makes their own autochangers for their large (?12"?) optical

Subject: [6.8.7] Sony {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Sony makes their own jukeboxes for their 12" WORMs and for 5.25" MO. is the place to

Subject: [6.9] CD-ROM Jukeboxes
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Subject: [6.9.1] Pioneer
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

From: (Mike Caplinger)
Subject: driver software for Pioneer DRM-5004X CDROM jukebox
Date: Tue Aug 23 10:09:00 PDT 1994
Organization: UTexas Mail-to-News Gateway
Lines: 13

Pioneer recently announced their DRM-5004X CDROM jukebox, which has
four quad-speed drives and holds 500 CDs for under $20,000.

Mike Caplinger

Pioneer also has a 6-disk mini-changer, where SCSI LUNs 0-5 correspond
to the individual disks; accessing one causes a mount. (Brian A Berg
<>, 1996/3/29)

There's also an 18-disk model. You can find info on all three at (rdv, 96/8/5)

Subject: [6.9.2] CyberTower {Brief, New}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries) has frustratingly little info on a product
that apparently is 7 CD-ROM drives made to behave like a single SCSI
target. Not really an autochanger, more of an array. Not sure who the
manufacturer is; the same unit is available from Procom (rdv,96/8/5)

Subject: [6.9.3] NSMJukebox {Brief, New}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries) describes what they call "the universe's
fastest CD-ROM jukebox". 150 platters (90GB), up to four drives. (rdv,

Subject: [6.9.4] Nakamichi {Brief, New}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

A 4-disk changer built on into an 8x
reader. (rdv,96/8/5)

Subject: [6.9.5] CDI Juke Box Library {Brief,New}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

A 28-disk changer (standalone network server?) with up to four drives,
and a built-in PC w/ 128 MB RAM and a 1GB disk. Available from (rdv,96/8/5)

Subject: [6.9.6] K & S M-200 {Brief, New}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

A 200-disk autochanger. Available from (rdv,96/8/5)

Subject: [6.9.7] DISC {Brief, New}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

Makes large libraries (up to ~1,500 media slots and up to 32 drives);
see (Stephen Fister <fis...@Synopsys.COM>,

Subject: [6.9.8] Meridian {Brief, New}
From: Robotics (Autochangers, Jukeboxes, Stackers, Libraries)

CD Net Universal Server from Meridian,
Not really an autochanger, but an array of CD-ROM drives in a box with
an NFS or Netware interface. (rdv, 97/6/30)

Subject: [7] File Systems
From: File Systems

This topic is also discussed frequently in comp.os.research.

Subject: [7.1] NFS {Brief}
From: File Systems

The Network File System, originally developed by Sun Microsystems and
now pretty standard in the Unix world, and clients exist for PC, Mac,
VMS, and other non-Unix OSes. V2, the common version, supports single
files only up to 2^32 (4GB) bytes. I'm not sure if there are any
limits to a file system size under NFS, other than those imposed by
the client and server OSes (SHMO).

NFS is defined in RFC 1094. V3 is now RFC 1813.

There is at least one newsgroup devoted specifically to NFS:

Subject: [7.1.1] NFS V3
From: File Systems

NFS V3 supports 64-bit files and write caching.

The first implementation was from Digital with DEC OSF/1 V3.0 for
Alpha AXP. Silicon Graphics supports it on IRIX 5.3. Cray will support
it on UNICOS 9. I don't know about other vendors but I have heard
rumours that the releases coming in the second half of 1995 will
support it.

Further information on NFS V3 can be found from

(, 95/1/22)

Solaris 2.5, available Nov. 95, is reported to have V3 support.
Network Appliances have it as of 3.0, Sept. 95. ( (Guy
Harris), 95/10/6)

Subject: [7.2] AFS {Brief}
From: File Systems

The Andrew File System (SHMO). Allows naming of files worldwide as if
they were a locally-mounted FS (from cooperating clients, of course).

There's an "alt" group for AFS - "alt.filesystems.afs". Available
commercially from Transarc.

Subject: [7.3] DFS {Brief}
From: File Systems

Another remote file system protocol that supports large files. I don't
know anything about it, or if any implementations really exist yet.

Subject: [7.4] Log based file systems
From: File Systems

Further Information:
%z InProceedings
%K hpdb:Rosenblum91
%s (Thu Oct 17 11:12:07 1991)
%A Mendel Rosenblum
%A John K. Ousterhout
%T The design and implementation of a log-structured file system
%C Proc. 13th SOSP.
%c Asilomar, Pacific Grove, CA
%D 13 Oct. 1991
%P 1 15
%x This paper presents a new technique for disk storage management
%x called a log-structured file system. A log-structured file system
%x writes all modifications to disk sequentially in a log-like
%x structure, thereby speeding up both file writing and crash
%x recovery. The log is the only structure on disk; it contains
%x indexing information so that files can be read back from the log
%x efficiently. In order to maintain large free areas on disk for
%x fast writing, we divide the log into segments and use a segment
%x cleaner to compress the live information from heavily fragmented
%x segments. We present a series of simulations that demonstrate the
%x efficiency of a simple cleaning policy based on cost and benefit.
%x We have implemented a prototype log-structured file system called
%x Sprite LFS; it outperforms current Unix file systems by an order of
%x magnitude for small-file writes while matching or exceeding Unix
%x performance for reads and large writes. Even when the overhead for
%x cleaning is included, Sprite LFS can use 70% of the disk bandwidth
%x for writing, whereas Unix file systems typically can use only
%x 5--10%.


Also, these papers:

Ousterhout and Douglis, "Beating the I/O Bottleneck: A Case for Log-
structured File Systems", Operating Systems Review, No. 1, Vol. 23, pp.
11-27, 1989, also available as Technical Report UCB/CSD 88/467.

Rosenblum and Ousterhout, "The Design and Implementation of a Log-
Structured File System", ACM SIGOPS Operating Systems Review, No. 5, Vol.
25, 1991.

Seltzer, "File System Performance and Transaction Support", PhD Thesis,
University of California, Berkeley, 1992, also available as Technical
Report UCB/ERL M92.

Seltzer, Bostic, McKusick and Staelin, "An Implementation of a Log-
Structured File System for UNIX", Proc. of the Winter 1993 USENIX Conf.,
pp. 315-331, 1993.

listed from the man page for mount_lfs under FreeBSD-2.1.5. (rdv, 97/1/17)

Subject: [7.5] Mainframe File Systems
From: File Systems

The WWW FAQ contains some information about mainframe file systems.

Subject: [7.6] Parallel System File Systems
From: File Systems

This discussion comes up occassionally on comp.arch and
comp.os.research. I don't know which newsgroups/mailing lists the PIO
(Parallel I/O) people hang out in, but it doesn't seem to be here.
They show up occassionally in comp.sys.super and comp.parallel. They
do have their own conferences, though.

The important work seems to be going on with the supercomputing gang
-- LLNL, CMU, Caltech, UIUC, Dartmouth, ORNL, SNL, etc. Work is also
being done by the parallel database community, including vendors such
as Teradata.

A paper presented at the ACM International Supercomputing Conference
in 1993 showed what to me seemed to be pretty appalling performance
for reading data and distributing it to multiple processors on an
Intel Delta supercomputer (sorry I don't have the reference in front
of me). (rdv, 94/8/12) The paper is old, now, and the Intel guys say
they have improved performance to up to 130 MB/sec. on the new Paragon
using their Parallel File System (PFS).

There is an excellent web site on parallel I/O at Dartmouth:

There is also a mailing list housed at Dartmouth,

The annual conference is I/O in Parallel and Distributed Systems
(IOPADS); 1997's is co-located with Supercomputing '97 in San Jose,
Nov. 17. Papers are due March 25, 1997. See

Subject: [7.7] Microsoft Windows NT {Brief}
From: File Systems

I seem to recall that NT supports 64-bit file systems for its own
native file systems? Anybody know for sure (SHMO)? (rdv, 94/8/24)

From *Inside the Windows NT(TM) File System*, by Helen Custer:

"NTFS allocates clusters and uses 64 bits to number them,
which results in a possible 2^64 clusters, each up to 4KB. Each
file can be of virtually infinite size, that is, 2^64 bytes

"Clusters" can be between 512 and 4K bytes.

The Win32 API supports 64-bit file sizes, albeit in a cheesy fashion
reminiscent of V6 UNIX - no 64-bit integral types used, just pairs of
32-bit integral types. ( (Guy Harris), 95/10/6)

Subject: [7.8] Large Unix File Systems
From: File Systems

There is now an industry group working on standardizing an API for
files larger than 2 GB (the max size normally supported on most Unix
systems). More info as I get it. The WWW-enabled can have a look at and see the various
proposals on the table.

Note that it is VERY easy to confuse whether an OS supports _files_
larger than 2 GB or _file systems_ larger than 2 GB. My table lists
some of both (thanks to (Benjamin Z. Goldsteen),
Ed Hamrick ( and Peter Poorman (
for much of this information).

It is straightforward for systems with 64-bit integers to support
64-bit files; for systems with 32-bit integers it is more complex. On
most 32-bit systems the offsets passed around inside the kernel (most
importantly, at the VFS layer) the file offsets and sizes tend to be
passed as 32-bit (signed) integers, meaning no files >2^31.

On most systems, the argument to lseek is of type off_t, which (on
SunOS and Linux, and plausibly on OSF/1 and others) is declared in a
header file as "typedef long off_t;".

For clients to really have access to large files, three pieces are
required: local FS support, an appropriate network protocol, and
server support for 64-bit FSes. For FTP access, I believe _literally_
inifinitely large files are possible, but I'm not sure(SHMO). For NFS
access, NFS V2 supports only 2GB files. NFS V3, just becoming
available now, supports full 64-bit files, I believe (anybody have a
reference to the docs? RFC? SHMO). With the notable exception of
Unitree (which does not use, depend on, or appear as, a local FS on
the server), server support for 64-bit files is provided only when the
server's own local FSes are 64-bit.

Even for the systems that _do_ support large files, not all are
programmer or user-transparent for supporting large files. UniCOS is,
OSF/1 is, ConvexOS is not (there are two system calls, lseek and
lseek64, with 32-bit and 64-bit file offsets, respectively, though the
Fortran interface is transparent).

This brings up the related issues. A complete large files implementation
needs not only the system calls, but also the stdio library and the runtime
libraries for the languages (Fortran, Cobol,...). Further, system utilities
(sed, dd, etcetera) need to be capable of dealing with large files.

(It has been pointed out that the GNU C compiler runs on most of these
machines, so it is possible to use "long long" as a 64-bit int on
them, but what matters for file systems is the system compiler.)

Here's the start of a table on these. Really such a simple table can't
do the problem justice, but it'll give you an idea. Keep in mind that
many of these systems support many file system types; I've listed only
the most interesting so far from this point of view. I'd like to flesh
it out more completely, though.

1 GB = 2^30, 1 TB = 2^40, 1 PB = 2^50, 1 EB = 2^60
NYR = Not Yet Released

OS/hardware 64-bit C max max NFS info
datatype par- file V3 updated
tition size sup
size (bytes)
UniCOS (Cray vector) int, long ? 8 EB? ? 8/94
ConvexOS long long 1 TB 1 TB N 9/94
Alpha AXP OSF/1 V3.0
AFS long 128 GB 16 TB 8/94 9/94
Paragon OSF/1 ? 8 EB* 8 EB N 2/95
UTS (Amdahl) ? ? 8 EB? ? 8/94
HP/UX 9 (HP 9xxx) ? 4 GB ? ? 8/94
Silicon Graphics
IRIX 5.2 EFS long long 8 GB 2 GB N 9/94
IRIX 6.0 EFS long 8 GB 2 GB N 9/94 (NYR)
IRIX 5.3 XFS ?long long? ? ?TB? Y 9/94 (NYR)
AIX (IBM RS/6000)
4.1 JFS long long 64 GB 2 GB N 8/94
Solaris 2.x (Sun Sparc) long long 1 TB 2 GB (soon?) 9/94
BSD 4.4 long long ? 8 EB? ? 8/94
Linux long long 1 TB 2 GB ? 9/94
DG/UX 5.4 long long 2 TB 2 GB ? 9/94
Alliant Concentrix long long ?>2 GB ?>2 GB N 9/94 (dead)

* The Paragon PFS (Parallel File System), as I understand it, parallelizes
access to the files; each partition striped across is limited to 2GB, so
really the max partition size is 2GB * # of disks that can be attached.

A slightly more detailed
description of certain implementations
is available with the WWW version.

In addition, the HPSS (see above) supports large files, as does
Unitree (though the Unitree interface to them is limited).

Subject: [7.9] Non-Unix Large File Systems
From: File Systems

(info about non-Unix large FSes also welcome; SHMO)

OpenVMS (any version) supports 2TB files (32-bit unsigned block
number, 9-bit offset) through its RMS interface (still limited to 2GB
through the C run-time library), but file systems are limited to ~7GB
(as of Open AXP 1.5 and OpenVMS VAX 6.0 the max volume size has been
bumped to 1 TB). (from a friend, rdv, 94/8/26, and Rod Widdowson,
Filesystems group, OpenVMS engineering, Scotland).

Subject: [8] (Device) Interfaces
From: (Device) Interfaces

There is a new web site with lots of info at (rdv, 96/2/21)
Looks like it's class notes, so no idea how long it will stay up.
Don't forget to see

Subject: [8.1] SCSI {Full}
From: (Device) Interfaces

SCSI is the Small Computer System Interface. It is standardized by
ANSI X3T9.2. It is mostly aimed at storage devices, with command sets
defined for disks, tapes, and autochangers, but also includes
communications devices, printers, and scanners.

It's daisy-chained, with a maximum of eight devices (including the
host computer) on a single narrow bus (there are non-standard schemes
for 16 devices on a wide bus). Any device can be an initiator, so it's
possible to use the bus for sharing devices between hosts, provided
your software can manage it.

See also the newsgroup comp.periphs.scsi, especially for "How do I
hook up a Brand X diskdrive to my Atavachron 9000 PDA?" type

There is also an FTP site for some working documents for the SCSI-3
committees and other X3T10 documents. See or

You'll find good info at and at

Subject: [8.1.1] Single ended vs differential
From: (Device) Interfaces

This distinction is at the eletrical signalling level. However,
single-ended is limited to total bus lengths of 6.0 meters, while
differential can go up to 25 meters (SCSI-II). Differential is
generally more robust to noise and cross-talk, but the bus drivers are
more expensive. In theory no difference in transfer speed or
capabilities, but in practice the added noise margin could mean higher
_reliable_ transfer rates on your system, especially if your bus is

Most disk drives and most low-end products are available only with a
single-ended interface. A few devices are available with either as a
purchase option, and a few are switchable by the user.

The cables and connectors are the same for both, though the pinouts
are (naturally) somewhat different.

Plugging a single-ended device into a running differential bus or
vice-versa may result in damage to one or more devices. Most newer
devices have fuses or protection circuits utilitizing the DIFFSENSE
signal to prevent device damage.

There are now recommended icons used to distinguish between the two:

single-ended differential
/\ //\
/ \ // \
< -- << --
\ / \\ /
\/ \\/

Converters do exist that will allow you to hook up single-ended
devices to a differential bus and vice-versa. People who have used
them say they work great, but in theory they shouldn't work :-). As I
understand it, changing the signalling introduces delays in some of
the control signals that means that some devices could miss certain
signal transitions. The best advice is to borrow one and try it, and
see if it works in your system. One company's name is Paralan,

Subject: [8.1.2] Asynchronous vs Synchronous Transfers
From: (Device) Interfaces

Asynchronous transfers mean that every single byte must be
acknowledged before the next can be transfered. Synchronous means that
the device sending data can drop a series of transfers onto the bus,
toggling REQ or ACK (as appropriate), and then sit back and wait for
the corresponding pulses to return from the other device.

Async transfers, involving much more waiting, are correspondingly
slower. 2-4 MB/sec are good values for async transfers.

Sync transfer speeds are established during a negotiation between the
initiator and target, but devices are not required to use the full
speed they negotiate for. This speed represents the maximum burst rate
your device will use. Common values are 5 and 10 MB/sec.

In practice, virtually every modern device supports synchronous
transfers, but some implementations are better than others.

Subject: [8.1.3] SCSI-I vs SCSI-II vs SCSI-III
From: (Device) Interfaces

SCSI (now commonly known as SCSI-I) was the original 1986 standard,
X3.131-1986. It specified the electrical level and some of the
mid-layer issues involving messages and packet structure, but (I
believe, my memory's bad) didn't formalize the Common Command Set
(CCS), that was done independently. It supported a maximum burst rate
of 5 MB/sec. on an 8-bit bus.


Consult the SCSI standards documents, and the manuals for the device you
are working with for more information. The "SCSI 1" specification
document is called SCSI Specification, ANSI X3T9.2/86-109. Also of
interest is the Common Command Set specification document SCSI CCS
Specification, ANSI X3T9.2/85-3

SCSI-II received final approval in early 1994, but has been a de facto
standard for several years. The CCS was standardized for a variety of
different types of peripherals. The max allowable transfer rate was
raised to 10 MT/s (see below). A 16-bit bus (Wide SCSI) and 32-bit bus
(double-wide SCSI) are specified (see below).

SCSI-III is the latest effort, and involves more cleanly separating
the functionality into layers; the command layer is defined
independently from the physical layer. In addition to the traditional
parallel cable, there are efforts going on to define physical layers
for Fibre Channel and a more generic Serial SCSI. Thus, there will be
no SCSI-IV; only the individual pieces will be updated as necessary.

Subject: [8.1.4] Fast-Wide SCSI
From: (Device) Interfaces

The max allowable transfer rate was raised to 10 MT/s (mega-transfers
per second) in SCSI-2, referred to as Fast SCSI. Note that this is NOT
required, devices running at ANY speed below that may claim to be
SCSI-II compliant! Fast implies SCSI-II, not the other way around!
Fast Narrow is thus 10 MB/sec. Both the initiator (computer) and
target (peripheral) must support fast transfer for it to be of any
use, but intermixing fast and slow devices on a bus presents no
operational problems (only performance ones).

A 16-bit bus (Wide SCSI) and 32-bit bus (double-wide SCSI) are
specified in SCSI-2. The wide busses require the use of a second cable
in SCSI-2. The first cable is 50 pins, known as the A cable; the 2nd
is 68 pins, known as the B cable. I know of no one actually using
32-bit SCSI, but it would also run on an A/B cable pair. Slow (or
Normal) Wide is thus 5 MT/s * 2 Bytes/T, 10 MB/sec. Fast Wide is 20
MB/sec. Fast Double Wide would be 40 MB/sec.

In the SCSI-3 physical layer spec (SCSI-PH), a single 68-pin cable,
known as the P cable, is allowable for 8 or 16-bit busses. This is the
option most people who have implemented Wide SCSI have chosen for the
cabling, even though their upper layer is generally SCSI-2.

There is a small movement (heard here on the net occassionally) to
promote an Ultra-SCSI high-speed bus, with a burst rate of something
like 20 MT/sec on very short cables. At present it is unclear what
will happen to this effort. There is also talk, in conjunction with a
change to low-voltage differential signalling, to go to 40MT/sec.

Subject: [8.1.5] Shared Busses / Performance {Brief}
From: (Device) Interfaces

Also known as, "It's only a 500KB/sec. tape drive, why do I care if
the burst rate is only 2 MB/sec.?" or gets good marks for "plays well
with others".

Most of this is relevant to all shared busses, not just SCSI.
burst v. sustained performance, disconnect, command overhead, etc.

Subject: [8.1.6] Cabling/Hot Plugging {Brief}
From: (Device) Interfaces

Nominally not supported.

Subject: [8.1.7] Third Party Transfers/Separation of Control & Data Paths {Brief}
From: (Device) Interfaces

SCSI-2 has commands that support third-party copying of data; one
initiator tells device A to copy to device B. I don't know of any
devices actually using this.

Separation of control & data paths is a popular topic these days; can
somebody comment on whether or not SCSI-3 supports this? I don't think
so. (SHMO)

Subject: [8.2] IDE {Brief}
From: (Device) Interfaces
PC use
Does not support overlapped I/O.

Subject: [8.3] IPI {None}
From: (Device) Interfaces

Subject: [8.4] HIPPI {Brief}
From: (Device) Interfaces

32-bit transfers at 25 MT/sec., 100 MB/sec. High Performance Parallel
Interface is a unidirectional channel, i.e. you have to have an OUT
cable and and IN cable for bidirectional transfers (you could have
just one, if it's a read-only device like a scanner or write-only like
a frame buffer). HiPPI is not a shared bus, but its frames can be
switched through a crossbar switch (Network Systems is the premiere

HiPPI is used for supercomputer-to-supercomputer networking (TCP/IP,
no less), for RAID arrays (from Maximum Strategy, IBM and others),
tape drives (Sony ID-1 drive), frame buffers and increasingly
workstations (SGI and IBM support HiPPI, and 3rd-party Sbus cards
exist for Sun).

Due partly to the high overhead of HiPPI connections, many devices
have elected to separate the control path from the data path. A common
control path in that case is ethernet.

Good resources from the HiPPI Networking Forum on the web at

Subject: [8.4.1] HIPPI-6400 {Brief}
From: (Device) Interfaces

An effort aimed at reaching 6400 Mbps (800 Mbytes/sec.) around the end
of 1996.

From rev 0.15 of the HIPPI-6400-PH specification, dated March 4, 1996,
ftp'ed from

Looks like the copper interface will be a cable with 44 micro-coax
conductors, 22 in each direction. That's 16 data, 4 control, clock,
and frame. A micro-packet is 32 data bytes and 64 bits of control
information. I guess this means they're planning on 400 Mbps on each
data line. The fiber variant uses 12 multimode fibers (in each
direction, I presume, though it doesn't seem to say that): 8 data + 2
control + frame + clock, so presumably 800 Mbps on each fiber. Cable
lengths in both cases TBD.

Subject: [8.5] Ultranet {Brief}
From: (Device) Interfaces

Fiber to the host, a hub with a backplane running at a total rate of

Subject: [8.6] Ethernet {Brief}
From: (Device) Interfaces

Generally related to normal inter-host networking, but also used as
a control path for some HiPPI devices. Ampex also uses NetSCSI over
ethernet to control their autochangers. Also, obviously, used for
connecting many servers to their clients. Standard today is 10 Mbps,
100 Mbps (fast ethernet) is becoming more common.

Subject: [8.7] FDDI {None}
From: (Device) Interfaces

Subject: [8.8] Fibre Channel Standard (FCS)
From: (Device) Interfaces

Rich Taborek of Amdahl has created an excellent web page on Fibre
Channel at [Has draft Fibre Channel documents] [Has FCSI Fibre Channel Profiles]
(rdv, 95/5/18 from Louis Grantham <>)

Fibre Channel runs over coax or optical fibre (single or multimode),
and even twisted pair. Fibre Channel comes in two basic forms --
Aribtrated Loop and switched fabric, which aren't (yet)
interoperable. The host interfaces are rapidly becoming cheaper, but
the switches are still expensive.

Fibre Channel standards define several functional levels, from the
physical interface up to the mapping to upper level functionality,
e.g. how to do SCSI commands over FC. FC provides several "classes"
of service, including dedicated circuit and acknowledged and
unacknowledged datagrams. Can also be used for IP. (rdv, 96/10/28)

Subject: [8.9] ESCONN/SBCON {Brief}
From: (Device) Interfaces

Enterprise Systems CONNect. IBM's new mainframe attach -- fiber, I
believe. The standardized version of this is known as SBCON, and Rich
Taborek has once again created an excellent web page at

Subject: [8.10] IEEE P1394 (Serial Bus)
From: (Device) Interfaces

Apple's new standard for connecting devices via a high-speed serial
bus. Good info at Also some info FTPable at (I think that's where I got those papers.) (rdv,

After having been somewhat dormant for a while, standards activity on
new versions of 1394 is heating up again. Faster versions are in the
works, as is a protocol for doing disks across it. (rdv, 96/10/28)

Subject: [8.11] Serial Storage Architecture (SSA)
From: (Device) Interfaces

IBM's new offering in the serial device interface sweepstakes.
Some docs and tentative working standards available on the SCSI ftp
site: The SSA Industry
Association has a web server at Disk drives from
Conner and Micropolis, and Pathlight and Adaptec and expected to do
host adapters.

Subject: [8.12] S2I: IEEE P1285 Scalable Storage Interface
From: (Device) Interfaces

Chaired by Martin Freeman, Philips Research, this is an effort to
standardize attaching disk drives directly to a system bus, making the
disk's buffers readable as regular memory to the CPU. Sort of the
opposite of network-attached storage, this couples the storage device
design more closely to the hardware and OS of the host system. See for more info. (rdv, 1995/12/22)

Subject: [8.13] Multibus, Unibus, Mainframe Channels, and other history {None}
From: (Device) Interfaces

Subject: [9] Other
From: Other
Subject: [9.1] Video vs Datagrade tapes {brief, 5/94}
From: Other
cost vs reliability
Are datagrade really more reliable?
Warrantee of drive
Cleaning cycle of drive
Headlife of drive

Subject: [9.2] Compression
From: Other

See the comp.compression FAQ, and don't believe everything a vendor
tells you. 2x compression is the standard going rate for lossless
compression of arbitrary data, though some vendors claim 2.5 or 3x.
Your mileage will vary with your data type.

Compressing tape drives are common, but for disks and other block
devices I don't know of anything being done. The unpredictability of
the compression ratio generally makes it inappropriate for devices
that need fixed capacities and addresses.

Online compression of files can be accomplished by hand using
utilities such as gzip and Unix compress. Some systems support
software compression of files in the file system software, and will
transparently compress and decompress files as needed. Stacker for PCs
is one example; for Unix-like systems this seems to be common research
for object-oriented file systems (including the GNU Hurd), but I don't
know of any production versions offhand (SHMO).

Compression may make your data more vulnerable to errors. A single
error early in a compressed stream of data can render the entire data
stream unreadable.

Subject: [10] Benchmarking
From: Benchmarking

See the comp.benchmarks FAQ, and don't believe everything a vendor
tells you.

There's a good paper on a new I/O benchmarking technique that also
covers the pitfalls of I/O benchmarking in the Nov. '94 ACM
Transactions on Computer Systems -- "A New Approach to I/O Performance
Evaluation -- Self-Scaling I/O Benchmarks, Predicted I/O Performance",
Peter Chen and David Patterson.

Bonnie, IOZONE, IOBENCH, nhfsstone, one of the SPECs (SFS), are all
useful for measuring I/O performance. There is also a program called
BENCHMARK available from -- apparently a
standardized set of scripts to test remote access to mass storage

In particular, note that based on a discussion here recently (8/96),
it appears that some magazines (who ought to know better) are using
HDT BenchTest as a disk drive performance measure, with the I/O sizes
set so small that the disk drive cache is covering them all, resulting
in anomalously high data rates (especially write rates). is the start of a
reasonable-looking benchmark for PC hard drives (posted by, 9/96)

==== SPEC SFS ====

SPEC's System-level File Server (SFS) workload measures NFS server
performance. It uses one server and two or more "load generator"

SPEC-SFS is not free; it costs US$1,200 from the SPEC corporation.
There's a FAQ about SPEC posted sometimes in comp.benchmarks.

Subject: [11] Mass Storage Conferences
From: Mass Storage Conferences

There are two main academic conferences devoted specifically to mass
storage (in addition to, of course, the supercomputer and OS
conferences, and interesting stuff in databases, optical
conferences, Usenix, SOSP...).

NASA Goddard Space Flight Center and the IEEE run two conferences, in
an 18-month or so alternating pattern.

You'll find my notes on the letest Goddard conference at

The contact for the NASA Mass Storage Conference (Sept. 17-19, 1996):

Jorge Scientific Corporation
7500 Greenway Center Drive
Suite 1130
Greenbelt, MD USA 20770

or if that fails email or There is some info available on the web at

Also, the latest IEEE was in September '95:

* The 14th IEEE Mass Storage Symposium was September 11-14, 1995 at
Monterey, CA. More info from Bernie O'Lear ( or
Sam Coleman (

Also of interest, there are the conferences on Very Large Database
Systems. I have a reference somewhere...

Interesting material shows up in the SPIE conferences.

Subject: [11.0.1] THIC Tape Head Interface Committee {Brief, New}
From: Mass Storage Conferences

I would like to bring to your attention the THIC Home Page at the URL and its anonymous ftp archives at the URL

THIC started out in the early 70's as the Tape Head Interface Committee
under the auspices of the DoD, but has since grown and expanded to embrace
most data recording technologies. THIC has been meeting four times a year,
alternating between the east and west coasts. The last meeting was in
Seattle WA on Jan 21 and 22, 1997, and the next will be on April 22 and 23
at the DoubleTree in Tysons Corner VA. The papers range from marketing,
new product announcement and discussion, to the problems of the various
recording technologies. Since October 1995, I have been trying to collect
as many of the papers as I could from each of the meetings and have been
placing them in Adobe PDF on the THIC archives at I also
maintain a no-frills home page where the agenda is displayed, with links to
papers which are available in the archives. (P.C. Hariharan, 97/2)

Subject: [12] MTBF (Mean Time Between Flareups, er, Failures)
From: MTBF (Mean Time Between Flareups, er, Failures)

There is a short FAQ-like document available from IBM at No math for the
statistically inclined, but explains in clear prose what IBM at least
means when they say MTBF.

I will also note that, for a complex but reparable system such as an
autochanger, each subsystem may have a separate MTBF and a different
lifetime, which may be combined to give one figure for the unit as a

Here is a reasonably understandable, but somewhat long, description of
MTBF. Thanks to Kevin Daly (president of Odetics,
wrote in 10/95 for this FAQ. After some waffling, I've included the
whole thing, despite its length.



In order to understand MTBF (Mean Time Between Failures) it is best to
start with something else -- something for which it is easier to
develop an intuitive feel. This other concept is failure rate which
is, not surprisingly, the average (mean) rate at which things fail. A
"thing" could be a component, an assembly, or a whole system. Some
things -- rocks, for example -- are accepted to have very low failure
rates while others -- British sports cars, for example -- are (or
should be) expected to have relatively high failure rates.

It is generally accepted among reliability specialists (and you,
therefore, must not question it) that a thing's failure rate isn't
constant, but generally goes through three phases over a thing's
lifetime. In the first phase the failure rate is relatively high, but
decreases over time -- this is called the "infant mortality" phase
(sensitive guys these reliability specialists). In the second phase
the failure rate is low and essentially constant -- this is
(imaginatively) called the "constant failure rate" phase. In the
third phase the failure rate begins increasing again, often quite
rapidly, -- this is called the "wearout" phase. The reliability
specialists noticed that when plotted as a function of time the
failure rate resembled a familiar bathroom appliance -- but they
called it a "bathtub" curve anyway. The units of failure rate are
failures per unit of "thing-time"; e.g. failures per machine-hour or
failures per system-year.

What, you may ask, does all this have to do with MTBF? MTBF is the
inverse of the failure rate in the constant failure rate phase.
Nothing more and nothing less. The units of MTBF are (or, should be)
units of "thing-time" pre failure; e.g. machine-hours per failure or
system-years per failure but the "thing" part and the "per failure"
part are almost always omitted to enhance the mystique and confusion
and to make MTBF appear to have the units of "time" which it doesn't.
We will bow to the convention of speaking of MTBF in hours or years --
but we all know what we really mean.

What does MTBF have to do with lifetime? Nothing at all! It is not
at all unusual for things to have MTBF's which significantly exceed
their lifetime as defined by wearout -- in fact, you know many such
things. A "thirty-something" American (well within his constant
failure rate phase) has a failure (death) rate of about 1.1 deaths per
1000 person-years and, therefore, has an MTBF of 900 years (of course
its really 900 person-years per death). Even the best ones, however,
wear out long before that.

This example points out one other important characteristic of MTBF --
it is an ensemble characteristic which applies to populations (i.e.
"lots") of things; not a sample characteristic which applies to one
specific thing. In the good old days when failure rates were
relatively high (and, therefore, MTBF relatively low) this
characteristic of MTBF was a curiosity which created lively (?) debate
at conventions of reliability specialists (them) but otherwise didn't
unduly bother right-thinking people (us). Things, however, have
changed. For many systems of interest today the required failure
rates are so low that the MTBF substantially exceeds the lifetime
(obviously nature had this right a long time ago). In these cases
MTBF's are not only "not necessarily" sample characteristics, but are
"necessarily not" sample characteristics. In the terms of the
reliability cognoscenti, failure processes are not ergodic (i.e. you
can't blithely trade population statistics for time statistics). The
key implication of this essential characteristic of MTBF is that it
can only be determined from populations and it should only be applied
to populations.

MTBF is, therefore an excellent characteristic for determining how
many spare hard drives are needed to support 1000 PC's, but a poor
characteristic for guiding you on when you should change your hard
drive to avoid a crash.

MTBF's are best determined from large populations. How large? From
every point of view (theoretical, practical, statistical) but cost,
the answer is "the larger, the better". There are, however, well
established techniques for planning and conducting test programs to
develop specified levels of confidence in a thing's MTBF.
Establishing an MTBF at the 80% confidence level, for example, is
clearly better, but much more difficult and expensive, than doing it
at a 60% confidence level. As an example, a test designed to
demonstrate a thing's MTBF at the 80% confidence level, requires a
total thing-time of 160% of the MTBF if it can be conducted with no
failures. You don't want to know how much thing-time is required to
achieve reasonable confidence levels if any failures occur during the

What, by the way, is "thing-time"? An important subtlety is that
"thing-time" isn't "clock time" (unless, of course, your thing is a
clock). The question of how to compute "thing-time" is a critical one
in reliability engineering. For some things (e.g. living thing) time
always counts but for others the passage of "thing-time" may be highly
dependent upon the state of the thing. Various ad hoc time
corrections (such as "power on hours" (POH)) have been used, primarily
in the electronics area. There is significant evidence that, in the
mechanical area "thing-time" is much more related to activity rate
than it is to clock time. Measures such as "Mean Cycles Between
Failures (MCBF)" are becoming accepted as more accurate ways to assess
the "duty cycle effect". Well-founded, if heuristic, techniques have
been developed for combining MCBF and MTBF effects for systems in
which the average activity rate is known.

MTBF need not, then be "Mysterious Time Between Failures" or
"Misleading Time Between Failures", but an important system
characteristic which can help to quantify the suitability of a system
for a potential application. While rising demands on system integrity
may make this characteristic seem "unnatural", remember you live in a
country of 250 million 9- million-hour MTBF people!

Kevin C. Daly
ATL Products
(714) 774-6900

Subject: [13] Mass Storage Reports
From: Mass Storage Reports

There are a number of consultants who also write regularly updated
in-depth reports (and sometimes post here) about various aspects of
the mass storage market; if you're going to get into this business or
are planning on spending many thousands or millions of dollars on
equipment, talking to one of them might be a good idea.

Sanjay Ranade ( is one of the ones who both writes
and posts here (he also has a couple of reasonably-priced books about
mass storage). Infotech's reports include HSM, network backup,
magtape and libraries.

Others include Disk/Trend (Mountain View, CA, 405-961-6209) (good info there) and Freeman Reports

Strategic Research Corporation has numerous white papers and good
links available at, including networked
storage. Some of them seem biased in particular directions, so caveat

Subject: [14] Network-Attached Peripherals {Brief}
From: Network-Attached Peripherals {Brief}

Coming soon. My own research is in this area; if you're lucky you
might find some pointers by going through my home page
http:// Contributions welcome.

Look for "A Brief Survey of Current Work on Network-Attached
Peripherals" in the January '96 ACM Operating Systems Review, by yours
truly. An expanded, updated version is available on the web at (rdv, 96/1/22) is Garth Gibson's Parallel Data
Lab, where they're doing excellent work on network-attached storage

At Lawrence Livermore, they're doing a network-attached RAID array to
integrate into HPSS; see

The ViewStation work at MIT, is concentrating on
ATM-attached peripherals, using ATM as a system-area network.

The Netstation project (which I work on
at ISI) is focusing on IP-connectible peripherals, using a gigabit
network as the system backplane.

Subject: [15] Other References
From: Other References

Subject: [15.1] Print
From: Other References

Computer Technology Review magazine, 310/208-1335, free to some.
Electronic News, weekly, 800/722-2346.
MacWeek, June 7, 1993, Page 36+
IEEE Computer had a full issue in March 94 on I/O subsystems

There are also two books by Sanjay Ranade (, who
posts here occassionally. One is _Mass Storage Technologies_
(1991ish?), the other, newer one is _Mass Storage Systems_. I've read
the first one, it's a little short on detail but a good overview.

Subject: [15.2] Web
From: Other References standards and tons of info. performance reports, media surveys, etc. Goes into a
lot of detail on topics such as archival stability.
lists some resellers and manufacturers of storage. has good information about PC hardware,
including old interfaces, floppies, controllers, etc. It has a LONG
list of specs for hard drives. also has good info on
hard drives and CD-ROM drives. lists storage products and
market projections.

Subject: [15.3] Newsgroups
From: Other References

You're in the primary one ( You'll also find info
in the groups on SCSI, PC hardware, and specific operating systems.
I'll try to add pointers to their FAQs soon.

The FAQ for can be found at

Subject: [15.4] Research Papers
From: Other References

I'm collecting reviews and a list of papers now, I expect to add it in
a few weeks. Contributions/suggestions welcome.





storage system issues, both software and hardware


To facilitate and encourage communication among people interested in computer
storage systems. The scope of the discussions would include issues relevant
to all types of computer storage systems, both hardware and software. The
general emphasis here is on open storage systems as opposed to platform
specific products or proprietary hardware from a particular vendor. Such
vendor specific discussions might belong in or comp.periphs.
Many of these questions are at the research, architectural, and design levels
today, but as more general storage system products enter the market,
discussions may expand into "how to use" type questions.


As processors become faster and faster, a major bottleneck in computing
becomes access to storage services: the hardware - disk, tape, optical,
solid-state disk, robots, etc., and the software - uniform and convenient
access to storage hardware. A far too true comment is that "A supercomputer
is a machine that converts a compute-bound problem into an I/O-bound
problem." As supercomputer performance reaches desktops, we all experience
the problems of:

o hot processor chips strapped onto anemic I/O
o incompatable storage systems that require expensive
systems integration gurus to integrate and
o databases that are intimately bound into the quirks of an
operating system for performance
o applications that are unable to obtain guarantees on when
their data and/or metadata is on stable storage
o cheap tape libraries and robots that are under-utilized
because software for migration and caching to
disk is not readily available
o nightmares in writing portable applications that attempt
to access tape volumes

This group will be a forum for discussions on storage topics including the

>1. commercial products - OSF Distributed File System (DFS)
based on Andrew, Epoch Infinite Storage Manager and
Renaissance, Auspex NS5000 NFS server, Legato
PrestoServer, AT&T Veritas, OSF Logical Volume Manager,
DISCOS UniTree, etc.
>2. storage strategies from major vendors - IBM System
Managed Storage, HP Distributed Information Storage
Architecture and StoragePlus, DEC Digital Storage
Architecture (DSA), Distributed Heterogeneous Storage
Management (DHSM), Hierarchical Storage Controllers, and
Mass Storage Control Protocol (MSCP)
>3. IEEE 1244 Storage Systems Standards Working Group
>4. ANSI X3B11.1 and Rock Ridge WORM file system standards
>5. emerging standard high-speed (100 MB/sec and up)
interconnects to storage systems: HIPPI, Fiber Channel
Standard, etc.
>6. POSIX supercomputing and batch committees' work on
storage volumes and tape mounts
>7. magnetic tape semantics ("Unix tape support is an
>8. physical volume management - volume naming, mount
semantics, enterprise-wide tracking of cartridges, etc.
>9. models for tape robots and optical jukeboxes - SCSI-2,
>10. designs for direct network-attached storage (storage as
black box)
>11. backup and archiving strategies
>12. raw storage services (i.e., raw byte strings) vs.
management of
structured data types (e.g. directories, database
>13. storage services for efficient database support
>14. storage server interfaces, e.g., OSF/1 Logical Volume
>15. object server and browser technology, e.g. Berkeley's
Sequoia 2000
>16. separation of control and data paths for high performance
by removing the control processor from the data path;
this eliminates the requirements for expensive I/O
capable (i.e., mainframe) control processors
>17. operating system-independent file system design
>18. SCSI-3 proposal for a flat file system built into the
disk drive
>19. client applications which bypass/ignore file systems:
virtual memory, databases, mail, hypertext, etc.
>20. layered access to storage services - How low level do we
want device control? How to support sophisticated, high
performance applications that need to bypass the file
>21. migration and caching of storage objects in a distributed
hierarchy of media types
>22. management of replicated storage objects
(differences/similarities to migration?)
>23. optimization of placement of storage objects vs. location
transparency and independence
>24. granularity of replication - file system, file, segment,
record, etc.,
>25. storage systems management - What information does an
administrator need to manage a large, distributed storage
>26. security issues - Who do you trust when your storage is
directly networked?
>27. RAID array architectures, including RADD (Redundant
Arrays of Distributed Disks) and Berkeley RAID-II HIPPI
>28. architectures and problems for tape arrays - striped tape
>29. stable storage algorithm of Lampson and Sturgis for
critical metadata
>30. How can cheap MIPS and RAM help storage? - HP DataMesh,
write-only disk caches, non-volatile caches, etc.
>31. support for multi-media or integrated digital continuous
media (audio, video, other realtime data streams)

This group will serve as a forum for the discussion of issues which do not
easily fit into the more tightly focused discussions in various existing
newsgroups. The issues are much broader than Unix (comp.1.*, comp.os.*),
as they transcend operating systems in general. Distributed computer systems
of the future will offer standard network storage services; what operating
system(s) they use (if any) will be irrelevant to their clients. The
peripheral groups (comp.periphs, comp.periphs.scsi) are too hardware oriented
for these topics. Several of these topics involve active standards groups
but several storage system issues are research topics in distributed systems.
In general, the standards newsgroups ( are too narrowly focused
for these discussions.

Subject: [17] Original Author's Disclaimer and Affiliation:
From: Original Author's Disclaimer and Affiliation:

This information is believed to be reasonably accurate although I do

not verify every submission. Neither the United Stages Government nor any
agency thereof, nor any of their employees, makes any warranty, express or
implied, or assumes any legal liability or responsibility for the accuracy,
completeness, or usefullness of any informatin, apparatus, product, or
process disclosed, or represents that its use would not infringe privately
owned rights. Reference herein to any specific commercial product, process,
or service by trade name, trademark, manufacturer, or otherwise, does not
necessarily constitute or imply its endorsement, recommendatin, or favoring
by the United States Government or any agency thereof. The views and
opinions of authors expressed herein do not necessarily state or reflect
those of the United States Government or any agency thereof.

Joseph Stith,, 708/840-3846
Assistant to the Computing Division Head -- IRM Planning
Computing Division, Fermilab, PO Box 500, MS 120, Batavia, IL 60510

Subject: [18] Copyright Notice
From: Copyright Notice

This compilation of material is copyright Rod Van Meter, Permission is granted to copy this material,
provided this copyright notice is retained. The contents are not to be
significantly modified without the express written consent of the

This is just to keep the various authors of this material from being
substantially misquoted or abused, not to restrict use of the

Permission to include this FAQ in published compilations (CD-ROM or
book) will be granted upon direct request.

Subject: [19] Additional Topics to be added
From: Additional Topics to be added

File Systems: Unix, IBM, VMS, Tops-20, Extent-based, Amiga, Mac
(resource & data forks)
FTP Sites
Volume Sets & Partitions
Important People/Mass Storage History
Books & Other Publications
Principles for Evaluating New Technologies
Performance Evaluation
seek time measurement
concurrent operations
queueing theory
Head Lifetime
Versioning in File Systems
Managing Risk
Media Migration/Managing Change
Physical v. Logical Addressing (seek optimizations, etc.)
Channels v. Busses
Intelligent Storage Subsystems
DEC's HSC-50 and star cluster for VAXen
Mainframe & Supercomputer I/O controllers
The broadcast and home audio/video / mass storage connection
Databases and Mass Storage
File System Research: watchdogs, named pipes, compressing FSes
The naming problem: Prospero
Distributed Locking & Update
Content-Addressable Storage & Other Unusual Ideas
The old film-storage system Sam Coleman talks about
Byte Ordering
Supercomputer Storage
Companies: Adstor, Avastor
I/O Benchmarks
User file systems
System CPU & bus loads for file system work
Memory-Mapped Files
Persistent Object Systems & their files
The VFS layer in Unix
What to look for in a backup product
Offsite Storage v. Network Backup
Test Equipment -- SCSI & HiPPI Analyzers
(reorganize along small user/large user/developer lines?)
(need to date every entry if possible)

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