On Mon, Oct 23, 2006 at 11:40:05AM +0200, Brice Figureau wrote:
>
> I'll try the data=writeback mount option. Is it possible to remount the
> partition and change the journal option on a running system?
Not with ext3, sorry.
>
> > Since mysql is probably triggering tons of fsyncs or O_SYNC writes,
> > you may want to increase the size of the ext3 log.
>
> Mysql is using O_DIRECT for its datafile. I don't know how it relates to
> the sync things, but I guess that to be truly ACID, it has to fsync the
> files on each transactions.
> How can I increase the ext3 log ?
> Any idea of the size I should use (and what is the default) ?
Even when using O_DIRECT, if the file is extended an FS commit is
triggered to record the extension.
>
> > If mysql is constantly appending to the files holding your tables, the
> > synchronous writes are more expensive and log intensive. Check your
> > setup to see if you can manually extend any of those files to avoid
> > constantly growing table files.
>
> The use of a battery-backed RAID cache should mitigate the sync writes,
> and since our mysql load is quite low, the machine shouldn't definitely
> freeze for seconds while copying files.
Ok, I would start with only doing data=writeback. That is probably a
big part of the problem.
-chris
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