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From: Terry Lambert <terry@lambert.org>
Message-Id: <199602052026.NAA14850@phaeton.artisoft.com>
Subject: Re: FAT filesystem performance
To: rnordier@iafrica.com (Robert Nordier)
Date: Mon, 5 Feb 1996 13:26:30 -0700 (MST)
Cc: hackers@FreeBSD.org
In-Reply-To: <199602050616.IAA03554@eac.iafrica.com> from "Robert Nordier" at Feb 5, 96 08:16:27 am
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> > Hmm... FAT can contain at most 64K of entries, each 2 bytes long, so
> > the needed amount of memory (if you cache raw FAT and don't try to make
> > any ``cooked'' version) must be at most 128Kbytes long. IMHO the raw FAT 
> > is enough convenient ant takes not very much of memory.
> 
> Agreed.
> 
> This is what the original author of the MS-DOS filesystem had to say on
> the subject of caching:
> 
>         The new MS-DOS [ie. DOS 2.0] does not keep the file
>         allocation tables in memory at all times.  Instead the
>         tables share the use of sector buffers....  This change
>         in the DOS goes completely against my original design
>         principles.... Now we're back to doing disk reads just
>         to find out where the data is.
> 			    -- Tim Paterson, Byte, June 1983.

That's because Tim didn't turn around and add a sector buffer cache.

Probably because DOS 2.0 was still fighting the 640k limit.  Let's
not limit ourselves because of absurd design decisions on the part
of DOS weenies... if they knew how to design an OS, we wouldn't
need FreeBSD.


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.