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
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