Poul-Henning Kamp wrote:
>
> In message <[EMAIL PROTECTED]>, Matt Dillon writes:
> >
> >:
> >:In message <[EMAIL PROTECTED]>,
>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.
> >:
> >:--
> >:Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
> >:[EMAIL PROTECTED] | TCP/IP since RFC 956
> >:FreeBSD committer | BSD since 4.3-tahoe
> >:Never attribute to malice what can adequately be explained by incompetence.
> >
> > 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.
> >
> > 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).
$ cd qmail-ldap/
$ grep fsync * | wc -l
21
$
Twenty-one times in qmail(-ldap) seems to be enough...
--
Andre
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