[Dovecot] Dovecot performance issues with many writes

[Timo Sirainen]

Do you have more than one Dovecot server? If only one, you can still disable the mail_nfs_* settings. Also it would be interesting to see nfsstat numbers from the Dovecot server, compared to those iostat numbers..

On 18.11.2011, at 0.38, Andy Robbins wrote:

> Well, the iostat command was run from the NFS server and dovecot was run from the mail server where it is mounted, hence the discrepancy there.
> 
> 
> On Thu, Nov 17, 2011 at 4:34 PM, Timo Sirainen <tss at iki.fi> wrote:
> On 18.11.2011, at 0.20, Andy Robbins wrote:
> 
> > # iostat -d 5 -x
> > Device:         rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s avgrq-sz
> > avgqu-sz   await  svctm  %util
> > dm-4              0.00     0.00  485.80  865.80  3886.40  6926.40
> > 8.00    28.69   19.63   0.70  94.00
> > drbd0             0.00     0.00  485.80  865.80  3886.40  6926.40
> > 8.00   111.42   94.44   0.74  99.60
> 
> These devices don't look like NFS, but you have:
> 
> > mmap_disable: yes
> > mail_nfs_storage: yes
> > mail_nfs_index: yes
> 
> So what filesystem is that? Are they storing only mails, or other stuff too (like logs)? The mail_nfs_*=yes are probably not needed and are slowing things up at least somewhat..
> 
> > lda:
> >  fsync_disable: no
> 
> This is explicitly set for LDA, but it's the default already elsewhere. Maybe you wanted to try fsync_disable=yes elsewhere except in LDA?
> 
> 
>