Re: Not using all of AIT tape

[Jesse Peterson]

Hi Billy,

Interesting problem. As you suggested I would definitely try changing the blocksize. But I'd also ask: have these tapes been used by any other programs? IOSCSITape doesn't yet support the mode pages for "tape partitioning" and I've heard that some backup tools (like Retrospect) use that on the tapes they write to. Try erasing tapes in those programs first, if that applies to your situation.

AIT tape at 40/104 GB would be AIT-1 Turbo I think. 40/104 is a 2.6x compression rate which is a little optimistic on Sony's side. My rule of thumb is 1.5x or 60GB on these tapes. Your mileage may vary of course with whatever type of data your writing.

Thanks,

- Jesse

On Nov 8, 2013, at 9:40 AM, Billy Bryce wrote:

Hello!

I have been using your IOSCSITape Driver (0.1) and its been going somewhat well. I've hit a small snag im hoping you can help me with. The drive im using is a SONY AIT: SDX460V drive with an IDE interface. It is hooked into a PowerMac G4 running Mac OS X Leopard 10.5.8. The drive accepts AIT-T tapes that go up to 104GB (Compressed) capacity.

The snag? I only seem to be able to write data up to 40GB (The tape's native capacity). Anything over this throws this error: "Function not implemented". and the console would give this: "rst0: SENSE: No Sense (Key: 0x0, ASC: 0x00, ASCQ: 0x02)" which, according to a google search means "End of medium!"

I checked the drive's DIP switch board and switch 7 (Data Compression Control) and 8 (Host-Controlled Data Compression Control OFF (Auto-Compress?) are both ON

Can you offer any assistance in helping me be able to write more than the native capacity to these tapes please?

They are going to be used for entire system backups that are over 40GB in size. Perhaps i need to change the block size?

-Thanks

PS, if it helps, here is the result of querying the tape drive status:

PowerMac-G4:Billys PowerMac G4 Billy$ mt -f /dev/rst0 statusSCSI tape drive, residual=0

ds=5<>

er=0

blocksize: 512 (0, 0, 0, 0)

density: 57 (0, 0, 0, 0)

current file number: -1

current block number: -1

[Billy Bryce]

Hello!

Odd, changing the block size did absolutely nothing, I changed it to 128 from its original 512 setting and the tape still reached the end before all of the file was on it. I did notice something that Sony mentioned, some files simply don't compress good and if they are compressed already then they may not compress further so that MIGHT explain this situation where a compressed DMG won't compress further so when there's 38-40gigs copied, tape reaches the end as that's its native capacity.

I wonder if using the TAR compression switches if that'll help squeeze a few hundred extra megabytes or web gigabytes onto the tape.

Also, to format the tapes I am using the Sony Tape Tool from the command line.

Jesse, I wonder if it will help you any, I got a demo copy of BRU PE (to

See if that would solve compression issue, it did not) with the terminal executables used to write to tapes if I want to use the command line, would these help you in any way with your own project? (Perhaps seeing how they manipulate the drive/etc) 

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[Jesse Peterson]

That would definitely do it -- attempting to compress already compressed data. Try archiving to tape some not-so-compressed data.

Also - feel free to use larger blocksizes. Like 128-kilobytes large. The tape should stream much quicker with larger block sizes.

Thanks,

- Jesse

On Nov 10, 2013, at 3:04 AM, user...@gmail.com wrote:

Gah...Sorry if im making a mess here, all i wanted to do was a spelling correction. (...A few hundred extra megabytes or a FEW gigabytes onto the tape...)

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