Date: Tue, 6 Feb 2001 16:04:22 -0200 (BRDT) From: Rik van Riel <riel@conectiva.com.br> To: Matt Dillon <dillon@earth.backplane.com> Cc: 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: <Pine.LNX.4.21.0102061601420.1535-100000@duckman.distro.conectiva> In-Reply-To: <200102061739.f16HdOB61963@earth.backplane.com>
next in thread | previous in thread | raw e-mail | index | archive | help
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. 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. regards, Rik -- Linux MM bugzilla: http://linux-mm.org/bugzilla.shtml Virtual memory is like a game you can't win; However, without VM there's truly nothing to lose... http://www.surriel.com/ http://www.conectiva.com/ http://distro.conectiva.com/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?Pine.LNX.4.21.0102061601420.1535-100000>