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

[email builder]

> Oh, and of course it also depends on Dovecot configuration :) Authentication 
> cache is needed and login processes must be in high performance mode.

I.e., I think:

http://wiki2.dovecot.org/LoginProcess
http://wiki2.dovecot.org/Authentication/Caching

> There is 

> still the extra work of forking a new imap process (could also be avoided with 
> yet another config option)

Are you referring to client_limit or service_count or something else as yet undeveloped?
Speaking of which, I cannot understand the different between those two.  Hints in the
configuration file (10-master.conf) and the wiki make them sound like they do the same
thing -- ??