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VFAT vs FAT32

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Burkhard Daniel

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Jan 28, 1997, 3:00:00 AM1/28/97
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Hi,

sorry if this is misplaced in this newsgroup, but I'mn sure some of
you can explain to me the difference between FAT32 and VFAT, if there
is any. I've read that FAT32 can handle paritions larger that 2GB, but
I know for sure that VFAT can't. So I guess there is a difference.
What is it?

Thanks,

Burkhard.
--
E-Mail: bu...@berlin.snafu.de
Homepage: http://www.inx.de/~burk
CompuServe: 100342,2050
Snail-Mail: Burkhard Daniel
Koepenicker Allee 40
D-10318 Berlin
Germany
Telephone: +49-30-508-11-25

"Who laughs last, at least dies happily."

J. Edward Sanchez

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Jan 28, 1997, 3:00:00 AM1/28/97
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bu...@berlin.snafu.de (Burkhard Daniel) wrote:

>Hi,
>
>sorry if this is misplaced in this newsgroup, but I'mn sure some of
>you can explain to me the difference between FAT32 and VFAT, if there
>is any. I've read that FAT32 can handle paritions larger that 2GB, but
>I know for sure that VFAT can't. So I guess there is a difference.
>What is it?

You have your terminology mixed up. FAT12 is the original DOS file
system, now used only on diskettes. FAT16 is the file system from DOS
2.x that is used on hard disks. FAT32 is the file system from Windows
95 OSR2 that can be used on large hard disks (512MB and up).

VFAT is the name of the installable file subsystem present in Windows
for Workgroups 3.11 and Windows 95. It allows the operating system to
read and write data in FAT partitions. The VFAT in Windows for
Workgroups 3.11 and the original Windows 95 supported FAT12 and FAT16.
Windows 95 OSR2's VFAT supports the new FAT32 as well.

Note that Windows 95's long filenames and extended attributes are
supported on FAT12, FAT16, and FAT32 partitions, as long as you use
Windows 95's VFAT subsystem to access the files.

For more information on FAT32, see KB article Q154997:

http://www.microsoft.com/kb/articles/q154/9/97.htm

HTH,
Edward

--
J. Edward Sanchez <je...@lightlink.com>
http://www.spiresoft.com/ (SoftArts)
http://www.spiresoft.com/jess/ (Edward's Place)

François Gouget

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Jan 29, 1997, 3:00:00 AM1/29/97
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J. Edward Sanchez wrote
>
> bu...@berlin.snafu.de (Burkhard Daniel) wrote:

> >[what is FAT, VFAT, FAT32... ]

In some details:

FAT comes from File Allocation Table which is a table describing
which sectors belong to a specific file storing for each sector the
number of the next sector (so this is a series of singly linked
lists).
FAT12 encodes the sector number in 12 bits, FAT16 does so in 16
bits and the brand new FAT32 uses 32bits.
With this mapping a FAT12 partition can be as big as 2^12*512/1024=
2MB and FAT16 partitions can achieve 32MB.
This is why Microsoft introduced what I would call the FAT16+ format
where the "unit of allocation", the thing that is designated by one
entry in the FAT, is not one sector but a cluster of sectors. All
current partitions use the FAT16+ format (or maybe you have very small
partitions). But clusters can only be as big as 64 sectors (32KB) which
yield the 2GB limit (2^16*64*512 bytes).
By using 32 bits to encode the sector number the limit would become
2TB but the FAT would become awfully large. For a 2GB partition using
clusters of one sector the FAT should be 64MB large !
For comparison a FAT12 FAT takes up to 2^12*1.5=6^KB bytes, FAT16 up
to 128KB and FAT32 up to 16GB ! Note the "up to", the FAT is only as big
as is necessary for partition.

> VFAT is the name of the installable file subsystem present in Windows
> for Workgroups 3.11 and Windows 95.

VFAT is not primarily the name of the Windows module that handles
FAT filesystems.
VFAT is a way of encoding long filenames on a FAT filesystem (be it
FAT12, FAT16 or FAT32). In particular, the Windows for Workgroup module
that handles FAT partitions does not support VFAT.

What strikes me is that Microsoft dares to introduce a new
filesystem format which is incompatible with low level programs anyway
but which is no better than the original FAT which is almost as bad as a
filesystem can be. By bad I mean inefficient for file accesses (to read
the last sector of a file you must go through the entire linked list,
fragmentation avoidance is inexistant, crash resiliance is low (only two
copies of the FAT but on the same track)...
For a description of a good filesystem read "The Design and
Implementation of the 4.4BSD Operating System" which describes the FFS
(Fast File System).

-----
Francois Gouget
fgo...@club-internet.fr

J. Edward Sanchez

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Jan 30, 1997, 3:00:00 AM1/30/97
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François Gouget <fgo...@club-internet.fr> wrote:

>J. Edward Sanchez wrote


>> VFAT is the name of the installable file subsystem present in Windows
>> for Workgroups 3.11 and Windows 95.
>
> VFAT is not primarily the name of the Windows module that handles
>FAT filesystems.
> VFAT is a way of encoding long filenames on a FAT filesystem (be it
>FAT12, FAT16 or FAT32). In particular, the Windows for Workgroup module
>that handles FAT partitions does not support VFAT.

I'm afraid that is a very common misconception.

VFAT *is* primarily the name of the IFS in both Windows for Workgroups
3.11 and Windows 95. Under Windows for Workgroups 3.11, VFAT was more
commonly known to users as "32-bit file access", but VFAT was in fact
its internal, technical name. If you do not believe this, do a KB
search for "VFAT" and note how many WfWG3.11 articles turn up in your
search.

Under Windows 95, the VFAT IFS was extended to support long filenames
and extended attributes (creation time, last access time). However,
the name of the file system is still just FAT (FAT12, FAT16, or FAT32,
as the case may be).

Strictly speaking, the LFN and EA extensions are not modifications to
the FAT format itself, but to the directory format. There is no
official name for the FAT-with-extended-directory-info format, but
some people call it "LFAT" or "EFAT". Just be sure not to call it
"VFAT", because VFAT is already the name of the Windows installable
file system that reads FAT-formatted disks and partitions.

François Gouget

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Jan 31, 1997, 3:00:00 AM1/31/97
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J. Edward Sanchez wrote

> François Gouget <fgo...@club-internet.fr> wrote:
>
> >J. Edward Sanchez wrote
> >> VFAT is the name of the installable file subsystem present in Windows
> >> for Workgroups 3.11 and Windows 95.
[...]

> > VFAT is not primarily the name of the Windows module that handles
> >FAT filesystems.
[...]

> I'm afraid that is a very common misconception.
>
> VFAT *is* primarily the name of the IFS in both Windows for Workgroups
> 3.11 and Windows 95.

You're right. I check in both "Inside Windows 95" (Adrian King) and
"Unauthorised Windows 95" (Andrew Schulman) and while King in some very
specific places King may be misinterpreted, Schulman never uses VFAT as a
filesystem name.
Also it is clear the VFAT is the name of the module which handles FAT
filesystems in Windows 95. That is is called so in WfWg is normal since as
Schulman states, this module came from the then Chicago project.
I wonder where this usage came from.

Maybe the "vfat" filesystem in Linux should be renamed !!!

-----
Francois Gouget
fgo...@club-internet.fr

Burkhard Daniel

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Feb 3, 1997, 3:00:00 AM2/3/97
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Does anyone know where I get FAT32 (or is it part of Win95? In this
case it would have to be backwards compatible To FAT12 and FAT16. I
can't see how this would be done, though).
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