Date: Tue, 6 Feb 2001 09:50:35 -0800 (PST) From: Matt Dillon <dillon@earth.backplane.com> To: Poul-Henning Kamp <phk@critter.freebsd.dk> Cc: Charles Randall <crandall@matchlogic.com>, Dan Phoenix <dphoenix@bravenet.com>, Alfred Perlstein <bright@wintelcom.net>, Jos Backus <josb@cncdsl.com>, freebsd-hackers@FreeBSD.ORG Subject: Re: soft updates and qmail (RE: qmail IO problems) Message-ID: <200102061750.f16HoZD62214@earth.backplane.com> References: <36088.981481432@critter>
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:> softupdates disk may wind up unwinding 'more' of the last few moments
:> worth of operations then a normal filesystem would. And, I might add,
:> Reiser is the same way.
:>
:> The only way to guarentee that file data is written to disk, with any
:> filesystem no matter how it is mounted (even sync mounted filesystems),
:> is by calling fsync().
:>
:> So I would stick with softupdates.
:
:... provided that qmail calls fsync(2).
:
:--
:Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
It doesn't matter whether qmail calls fsync or not as far as using
softupdates goes. No filesytem will guarentee stable storage
with fsync(), so softupdates is not going to be too much worse then
other FS's. So one might as well use softupdates. When/if qmail gets
its act together and calls fsync() properly, softupdates will guarentee
a level of consistency that only ReiserFS or XFS can even come close
to matching. A normal EXT2FS or FFS filesystem, even with fsync(),
*EVEN* with synchronous mounts, cannot guarentee file consistency
because it is still possible to corrupt the directory and loose the
file that was fsync()'d if a crash were to occur just after the fsync().
-Matt
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