[Dovecot] Significant performance problems

[Timo Sirainen]

On 7.10.2010, at 0.32, Chris Hobbs wrote:

> We currently see load averages spiking into the 20-30 range. When this happens, service crawls to a near standstill, and ultimately the SOGo client starts crashing out.

Is the load CPU load or disk I/O load? If I/O load, what NFS operations are peaking there, or all of them? Pretty graphs of nfsstat output would be nice.

> login_processes_count: 20

Probably could use less then 20.

> login_max_connections: 64

And this could be higher. In general you should have maybe 1-2x the number of login processes than CPU cores.

> mail_nfs_storage: yes

You said you have only one server accessing mails. So set this to "no".

> mail_location: maildir:~/Maildir:INDEX=/var/indexes/%u
..
> namespace:
>  type: shared
>  separator: /
>  prefix: shared/%%u/
>  location: maildir:%%h/Maildir:INDEX=~/Maildir/shared/%%u

The INDEX path here is wrong now.

Also you could try if maildir_very_dirty_syncs=yes is helpful.