dovecot - Sep 2009 - IMAP timeout problem

Hello,

We are running dovecot 1.1.2 on a Solaris 10 box.  We have been running the same
configuration for about a year without a problem.  We have a different cert for
POP and IMAP.

Recently we made two changes.  The cert for IMAP expired and we had to install a
new one.  We applied some patches to the SAN disks that hosts the mail
partition.  These changes were made over a weekend and the system was rebooted. 
There were no errors in the logs and everything worked fine until the following
Monday morning when IMAP connections increased.   When IMAP ports started
getting hammered in the morning, IMAP clients started getting "IMAP time
out" errors.    When this error occurs, IMAP freezes and IMAP clients such
as, Thunderbird and Squirrelmail  are not able to connect to the IMAP server
(both IMAP and IMAPS).   We cannot get a telnet connection to the IMAP port or a
openssl connection to the IMAPS port.  Kill -HUP of the dovecot server solves
the problem.  But again, when the usage increases, the problem surfaces again. 
There is no problem with POP or POPS.  It continues to function normally while
IMAP times out and freezes two or three times a day.

Any clue where the problem might be?  The debug log does not have any useful
pointers.

Thanks.

Vasantha

On Thu, 2009-09-03 at 13:23 -0700, Vasantha Narayan
wrote:
> We cannot get a telnet connection to the IMAP port or a openssl
> connection to the IMAPS port.  Kill -HUP of the dovecot server solves
> the problem.  But again, when the usage increases, the problem
> surfaces again.  There is no problem with POP or POPS.  It continues
> to function normally while IMAP times out and freezes two or three
> times a day.
How many imap-login processes do you have at those times? See if
changing login_* settings helps. http://wiki.dovecot.org/LoginProcess

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Vasantha Narayan wrote:
> Hello,
> 
> We are running dovecot 1.1.2 on a Solaris 10 box.  We have been
> running the same configuration for about a year without a problem.
> We have a different cert for POP and IMAP.
> 
> Recently we made two changes.  The cert for IMAP expired and we had
> to install a new one.  We applied some patches to the SAN disks that
> hosts the mail partition.  These changes were made over a weekend and
> the system was rebooted. 

Do you have any baseline benchmarks for your SAN?
What does vmstat 2 or iostat -c 2 say about i/o wait?

Ken

  There were no errors in the logs and
> everything worked fine until the following Monday morning when IMAP
> connections increased.   When IMAP ports started getting hammered in
> the morning, IMAP clients started getting "IMAP time out" errors.
> When this error occurs, IMAP freezes and IMAP clients such as,
> Thunderbird and Squirrelmail  are not able to connect to the IMAP
> server (both IMAP and IMAPS).   We cannot get a telnet connection to
> the IMAP port or a openssl connection to the IMAPS port.  Kill -HUP
> of the dovecot server solves the problem.  But again, when the usage
> increases, the problem surfaces again.  There is no problem with POP
> or POPS.  It continues to function normally while IMAP times out and
> freezes two or three times a day.
> 
> Any clue where the problem might be?  The debug log does not have any
> useful pointers.
> 
> Thanks.
> 
> Vasantha
> 
> 

-- 
Ken Anderson
Pacific Internet - http://www.pacific.net