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).
--
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.
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