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

[email builder]

Thank you very much for the fast reply.

>>  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.

Interesting.  What would be the motivations for disabling indexing?
Indexing is by default enabled?

Do you know what webmails are caching vs. non-caching?  

Am I correct that what you're pointing out is that with non-caching
webmails you will notice IMAP performance differences more readily
but that a caching webmail application might be better no matter
which IMAP server because it reduces the need for webmail to make
IMAP connections?

>>  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.

Ah, I didn't know about Director.  That looks very nice.  I had in mind that
we would have to use Perdition, but an integrated solution might be good.

Anyone have any thoughts or opinions considering Perdition vs. Director?

Full text searches don't hurt performance too bad?

Thanks for the other links, I will certainly go read up on them.