[Dovecot] Dovecot performance under high load (vs. Courier)

[Timo Sirainen]

On 21.6.2012, at 23.48, Reindl Harald wrote:

>> Someone benchmarked Dovecot a while ago in this list with and without imapproxy and the results showed that imapproxy simply slowed things down by adding extra latency. This probably isn't true for all installations, but I don't think there's much of a difference either way.
> 
> depends on network-latency, parallel users and last but
> not least count of folders - if you have 30 folders and
> roundcube refreshs every 20 seconds it will make in the
> worst case 180 connections for one user per minute
> 
> maybe a bechmark with high load shows other values
> 
> but felt performance in our setup is much better with
> imapproxy in front - roundcube feels like a desktop client

Oh, and of course it also depends on Dovecot configuration :) Authentication cache is needed and login processes must be in high performance mode. There is still the extra work of forking a new imap process (could also be avoided with yet another config option) and some other extra CPU usage, but those shouldn't cause much of a difference.

The extra network latency during login is a good point though.