On 09/18/2013 02:11 AM, Peter Peltonen wrote:
I've noticed some slowness on one of my toasters.
Looking at stats collected by sar, I see 10-20% iowait during peak hours.
Running iotop I can see processes taking 100 % IO during disk write:
pdflush
kjournald
dovecot/imap
The disk setup is not optimal for mail server use: I have 3ware RAID
controller running RAID-5 with SATA disks. I have 3072M memory, no swap
used, 1200M cached. I would prefer not to change any hardware at this
point, so I am looking for other options such as tweaking Dovecot.
Reading http://wiki.dovecot.org/MailLocation/LocalDisk I see that one
option would be to disable fsyncing. But when looking at
/etc/dovecot/conf.d/10-mail.conf all I see is:
#mail_fsync = optimized
So no fsync_disable option there? Has anyone tried to modify this
parameter?
Any other advice? Perhaps moving webmails to another server would be one
option, I do see sometimes httpd also in the iotop listing taking cpu...
Regards,
Peter
The following should reduce the overall i/o on your QMT:
.) ext3/4 filesystem tweaks: dirindex, noatime
.) put /var/qmail/simscan (scanning work area) on tmpfs.
--
-Eric 'shubes'
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