Date: Tue, 06 Feb 2001 20:35:51 +0100 From: Andre Oppermann <oppermann@monzoon.net> To: Rik van Riel <riel@conectiva.com.br> Cc: Matt Dillon <dillon@earth.backplane.com>, Poul-Henning Kamp <phk@critter.freebsd.dk>, 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: <3A805217.1D045A00@monzoon.net> References: <Pine.LNX.4.21.0102061601420.1535-100000@duckman.distro.conectiva>
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Rik van Riel wrote: > > On Tue, 6 Feb 2001, Matt Dillon wrote: > > > QMail's FAQ is totally incorrect. No major filesystem -- be it > > FFS, EX2FS, Reiser, FFS+Softupdates, guarentees that when you > > write() and close() a file that the file will then survive a disk > > crash. All these filesystems guarentee is that if a crash occurs, > > when the system reboots the filesystems will be recovered into a > > consistent state. Softupdates is considerably better at guarenteeing > > this consistency (as is something like Reiser), but if you crash a > > 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. > > Reiserfs and ext3 have write-ahead logs and, AFAIK, fsync() > will not return until there is a commit point in the log. Also FFS/UFS will not return before the file and directory entry is written to the disk. > This means that fsync() will guarantee that the transactions > won't be unwound (unless I've overlooked some weird special > case situations where it is needed after all...). > > The only filesystems I can see being completely resilient > against these destructive roll-backs would be LFS and tux2. This doesnt matter. If your machine crashes while receiving a message you're never going to issue a SMTP 250 to the sending mail server and it will try again later. We don't care if this incomplete queue file survives or gets purged. -- Andre To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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