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Date:      Tue, 06 Feb 2001 20:18:27 +0100
From:      Andre Oppermann <oppermann@monzoon.net>
To:        Rik van Riel <riel@conectiva.com.br>
Cc:        Poul-Henning Kamp <phk@critter.freebsd.dk>, Charles Randall <crandall@matchlogic.com>, 'Matt Dillon' <dillon@earth.backplane.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:  <3A804E03.B1142434@monzoon.net>
References:  <Pine.LNX.4.21.0102061538290.1535-100000@duckman.distro.conectiva>

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Rik van Riel wrote:
> 
> On Tue, 6 Feb 2001, Poul-Henning Kamp wrote:
> > In message <5FE9B713CCCDD311A03400508B8B3013054E3F5D@bdr-xcln.is.matchlogic.com>, Charles Randall writes:
> > >The qmail FAQ specifically recommends against soft updates for the mail
> > >queue.
> > >
> > >http://cr.yp.to/qmail/faq/reliability.html#filesystems
> > >
> > >Is this incorrect?
> >
> > It seems to indicate that qmail doesn't use fsync(2) as much as
> > it should do.  If that is true, then yes, softupdates would mean
> > that a lot of things which qmail (mistakenly) think has been
> > written are in fact not on the disk.
> 
> If this is true, I guess qmail can be officially considered
> broken. IIRC SMTP requires you to wait until the data is on
> stable (non-volatile) storage until you are allowed to return
> SMTP 250...

Qmail is not broken and issues a SMTP 250 with the inode number of
the queue file when the fsync() call on that file has completed.

> The system call used to guarantee this is fsync (and friends?);
> if qmail doesn't use it but makes assumptions that aren't true
> on any decent OS out there ...

Qmail uses it extensivly. Qmail treats the queue as a transactional
database with roll-forward and roll-backs in the event of a crash.

-- 
Andre


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