dovecot - May 2009 - Dovecot Max Connections & mbox vs. maildir format - Recommendations?

>> 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

On 24. mai. 2009, at 20.13, V S Rao wrote:
> 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.

IIRC RHEL only supports EXT3, not XFS/JFS and so on. ext3 is nice with  
large directories only if dir_index is enabled (tune2fs -O dir_index / 
dev/something). If dir_index is not enabled, ext3 will perform quite  
terribly with some 1000+ files in a directory. Apart from that, I  
would guess maildir would be best both for IMAP and POP.

roy
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