[Dovecot] Dovecot Max Connections & mbox vs. maildir format - Recommendations?

[V S Rao]

>> I had big issues with timeouts until I realize the the imap and mbox format
>> isnt a good choice if your users have huge naiboxes.
>> At my server there were users with mailboxes arount 700MB to over 1GB. each
>> time one of those users checked their email
>> the imap server had to open this huge file and parse it, causing I/O issues.

>> The only solution I found it was switch from mbox format to maildir format.

I am changing the subject line to reflect the discussion.

I too have a similar case with large mailboxes. My user mix is 70% POP3 vs. 30% IMAP. Would maildir still be the best recommended format? What is the opinion of the experts here?

The reason I am asking is that I am preparing to upgrade my mail server to RHEL 5.3. That would mean my Dovecot will be atleast 1.0.7, which should not be bad. If the recommendation is that I go from mbox format to Maildir, I want to plan that as well. However I don't want to land up in a situation where, I have to move back from Maildir to mbox again. So please do advice me on the best.

BTW one question: Assuming that my server has enough resources, ( 8 CPU @ 3.0GHz, 8GB RAM, 2Gbps FC Storage directly attached to the server & Gigabit NIC) what is the maximum number of concurrent connections that Dovecot can handle POP3 + IMAP combined? And I am asking for all the processes combined:

POP3-login processes
IMAP-login processes
POP3 sessions
IMAP sessions

Any TCP/IP kernel parameters to be tuned? or maybe in dovecot.conf?

Any advice will be immensely valuable to me while doing the migration.

Thanks and Regards
V S Rao