dovecot - Aug 2010 - hunting timeouts

Hi guys,

I inherited a Dovecot 1.0.1, which I will have to upgrade, but until then I
need, if possible, to resolve a timeout.

- we have about 25 IMAP users
- the busiest user has about 100 000 messages (Maildir) in less than 100 folders
- the mail server is on HP server with server grade 2.5" HDDs in RAID 5
- the load average of the server is low (the 5/15 minute is under 0.20)
- the mail server is in-house on Gigabit Ethernet

The timeout we face is that sometimes even small messages take 20-40 seconds to
open (i. e. Tunderbird 2 on Windows 7).
Or connection to the mail server timeouts.


Could you give me a few tips where can I look in order to detect the possible
reason for these timeouts.


Thank you, Iv

On Thu, 2010-08-12 at 14:28 +0200, Iv Ray wrote:
> The timeout we face is that sometimes even small messages take 20-40
seconds to open (i. e. Tunderbird 2 on Windows 7).
> Or connection to the mail server timeouts.
> 
> Could you give me a few tips where can I look in order to detect the
possible reason for these timeouts.
Have you looked at if during the 20-40 seconds the disk I/O is high? If
the problem is on server and not on network, it might be helpful to
strace the process that's taking a long time to reply. Then it could
show if it's mainly waiting for some system call to finish.
http://wiki.dovecot.org/Debugging/ProcessTracing