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Kiev Lo (lok@cuug.ab.ca) wrote:
: 	I have a new system with a HD formated with FAT32 under Windoze 95),
: I was wondering if there's any advantages of having a 32-bit file allocation
: table besides that fact that you can have bigger partitions?  Also, can a
: primary FAT32 partition and a extended FAT16 partition co-exist under win95?
: (would that make the system become unstable?)  The reason why I'm asking
: is that
: I'm planning to install Linux and I'm not sure if I can mount a FAT32 dos
: partition under Linux.  <sigh>  Only if we live in a Linux-dominated world.

Linux supports all these equally well (equally poorly?). Just don't
use compression on them. Linux is just starting to support compressed
DOS file systems and I don't think its very stable yet.

I would never use any of those DOS disk compressors anyway myself,
even if I never ran Linux, but some people like the idea.

On 13 Mar 1997 23:17:50 -0700, millerl@cuug.ab.ca (Lloyd Miller) wrote:

>Linux supports all these equally well (equally poorly?). Just don't
>use compression on them. Linux is just starting to support compressed
>DOS file systems and I don't think its very stable yet.

Nah, I never use any compressions on my HD.  It's too much of a hassle and it's
not really worth the trouble, esp since prices for $/mb has dropped so much
nowadays.  Besides, drivespace won't compress a drive paritioned with a FAT32
filesystem anyways.

>I would never use any of those DOS disk compressors anyway myself,
>even if I never ran Linux, but some people like the idea.

I don't think they'll be reliabel either.
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Kiev Lo (lok@cuug.ab.ca) wrote:
> I was wondering if there's any advantages of having a 32-bit file allocation
> table besides that fact that you can have bigger partitions?  Also, can a

The difference is technically not that the 32-bit FAT lets you have bigger
partitions, technically it is *required* for bigger partitions.  It also
results in more "dead space" on your hard-drive.

This is due to how the FAT file system works, it divides the partition
into clusters, for a 12-bit FAT you can have 4094 clusters, 16-bit can
have 65534 clusters.  Your cluster size (in bytes) will be some multiple
of 512 (which is called a block).  Each entry in the FAT table consumes
extra space (4bytes for a 32bit FAT, 3 for 24bit, 2 for 16bit).

It is quite typical to see clusters on DOS/windows systems where the
cluster size is 4096 bytes.  This results in an average wasted space of
2048 bytes per file.  I have also seen 16K clusters, which result in
an average of 8K/file of wasted space.

On unix systems a bitmap is used to replace the FAT which consumes much
less space than the FAT table would, as well, unix systems use blocks as
the smallest chunk of data, resulting in an average of only 256/file of
dead space.

So, on a system with 10000 files your wasted space would be:

DOS/win 4K clusters  = 2048 * 10000 = 20480000 = 20 MB
DOS/win 16K clusters = 8192 * 10000 = 81920000 = 80 MB
unix 512 byte blocks =  256 * 10000 =  2560000 =  2 MB

Unix wastes at least 1/10 less space than DOS/win.

Cheers,
Camz.


-- 
Martin Zimmerman               QNX FAQ Keeper   camz@passageway.com
Camz Software Enterprises     Work In Realtime  www.cuug.ab.ca:8001/~zimmerm/  
QNX Programming & Consulting    Work In QNX     www.passageway.com/camz/qnx/

camz@wooga.cuug.ab.ca (Martin Zimmerman) wrote:
>Kiev Lo (lok@cuug.ab.ca) wrote:
>> I was wondering if there's any advantages of having a 32-bit file allocation
>> table besides that fact that you can have bigger partitions?  Also, can a

Yes.  Smaller cluster size.  Drawback; incompatible with other OSs
(including the original Win95) and most data recovery utilities.
Also, disk compression isn't supported on FAT32.  

Finally, SR2's exclusive DOS mode (aka MS-DOS 7.1) supports FAT32 but
does not include a Share.exe utility.

>The difference is technically not that the 32-bit FAT lets you have bigger
>partitions, technically it is *required* for bigger partitions.  

Clarification:  Partitions over 2G in size

>It also results in more "dead space" on your hard-drive.

Definately not; it has the reverse effect.

With FAT16, you can have no more than 64k of data clusters in a
volume, and as the volume size increases, so does the cluster size.

FAT32 allows more clusters, so cluster size can be smaller, and is
typically 4k.  Compare this with:

256M - 511M      8k on FAT16
512M - 1023M   16k on FAT16
1024M - 2047M  32k on FAT16
Over 2048M        N/A on FAT16

>This is due to how the FAT file system works, it divides the partition
>into clusters, for a 12-bit FAT you can have 4094 clusters, 16-bit can
>have 65534 clusters.  Your cluster size (in bytes) will be some multiple
>of 512 (which is called a block).  Each entry in the FAT table consumes
>extra space (4bytes for a 32bit FAT, 3 for 24bit, 2 for 16bit).

Yes, FAT32's FAT is bigger, which may cause some impact esp. if RAM is
low.  More clusters could potentially make the defrag process slower
but also more necessary.

Chris Quirke wrote:
> 
> camz@wooga.cuug.ab.ca (Martin Zimmerman) wrote:
> >Kiev Lo (lok@cuug.ab.ca) wrote:
> >> I was wondering if there's any advantages of having a 32-bit file allocation
> >> table besides that fact that you can have bigger partitions?  Also, can a
> 
> Yes.  Smaller cluster size.  Drawback; incompatible with other OSs
> (including the original Win95) and most data recovery utilities.
> Also, disk compression isn't supported on FAT32.
> 
> Finally, SR2's exclusive DOS mode (aka MS-DOS 7.1) supports FAT32 but
> does not include a Share.exe utility.
> 
> >The difference is technically not that the 32-bit FAT lets you have bigger
> >partitions, technically it is *required* for bigger partitions.
> 
> Clarification:  Partitions over 2G in size
> 
> >It also results in more "dead space" on your hard-drive.
> 
> Definately not; it has the reverse effect.
> 
> With FAT16, you can have no more than 64k of data clusters in a
> volume, and as the volume size increases, so does the cluster size.
> 
> FAT32 allows more clusters, so cluster size can be smaller, and is
> typically 4k.  Compare this with:
> 
> 256M - 511M      8k on FAT16
> 512M - 1023M   16k on FAT16
> 1024M - 2047M  32k on FAT16
> Over 2048M        N/A on FAT16
> 
> >This is due to how the FAT file system works, it divides the partition
> >into clusters, for a 12-bit FAT you can have 4094 clusters, 16-bit can
> >have 65534 clusters.  Your cluster size (in bytes) will be some multiple
> >of 512 (which is called a block).  Each entry in the FAT table consumes
> >extra space (4bytes for a 32bit FAT, 3 for 24bit, 2 for 16bit).
> 
> Yes, FAT32's FAT is bigger, which may cause some impact esp. if RAM is
> low.  More clusters could potentially make the defrag process slower
> but also more necessary.

OSR2 FAT32 may not support DrvSpace but there is an undocumented switch
which will give you 512Byte cluters instaed of 4k similar to DriveSpace
clusters.  Anyone adventurous enough to try it?
-- 
Gary White
Michigan, USA

mailto:gary.w@usa.net