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

[Timo Sirainen]

On 21.6.2012, at 21.05, email builder wrote:

> We are building a new system that will support a large number of users (high volume, high concurrent usage, etc).  We have played with Dovecot, but in most serious applications we have traditionally used Courier IMAP.  It's my (lay) understanding that with indexing and perhaps other things in Dovecot, it might perform better than Courier in larger environments like this.  Am I correct or is it less clear-cut?

If you disable index index files in Dovecot, its performance should be slightly better than Courier. With index files the performance is typically much better in Dovecot, especially if you use a (non-caching) webmail.

> Any tips on making the migration (not migrating an existing system, I mean migrating our paradigm - things to consider, things to watch out for)?

If you don't migrate any existing users, I guess this doesn't differ much from any other optimized Dovecot installation. Usually large installations (>1M users) use NetApp NFS + Dovecot director. You might also want to enable full text searches. http://wiki2.dovecot.org/PerformanceTuning lists some other things.