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Date:      Sun, 4 Feb 1996 15:39:17 -0700 (MST)
From:      Terry Lambert <terry@lambert.org>
To:        faulkner@asgard.bga.com (Boyd Faulkner)
Cc:        luigi@labinfo.iet.unipi.it, hackers@FreeBSD.org
Subject:   Re: FAT filesystem performance
Message-ID:  <199602042239.PAA08330@phaeton.artisoft.com>
In-Reply-To: <199602041854.MAA07227@asgard.bga.com> from "Boyd Faulkner" at Feb 4, 96 12:54:52 pm

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> Before Terry has a fit :-) , let me tell you what he once told me.
> One of the problems of implementing someone else's file system is 
> error recovery.  If you cache FAT and your power goes out, for example,
> the FAT on the disk is not consistent.  Aside from there being no fsck_msdos,
> if you then booted up in DOS, your filesystem would be inconsistent, and
> DOS doesn't like or expect that.  You can write a fast read-only FAT
> FS but you have to fail as FAT would fail, to be truly compatible.
> 
> Did I get that right, Terry? :-)

Mostly.

If you had delayed ordered writes, the cache could be write-through,
so it would work.

Then the problems become "no msdos_fsck" and "must order regular I/O"
and "cache in MACH is too large".


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



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