This is is follow up to my previous post about dovecot performance being slow.
BTW, thanks to all that replied.
For one month we have been trying to figure why suddenly dovecot was slow. We had two server's running dovecot with the same config and one was fine while the other wasn't very slow. The server that was slow was on a virtual server and we noticed some time errors in the logs and installed ntpd which didn't help the problem.
After trying to tweak the config etc... I put dovecot on a new server and its running great.
Before I was seeing 35% idle cpu with 700 + pop3 login sessions and another 400 imap. Since we moved to a new server, that has no time issues, we are seeing 97% idle cpu with 50 - 70 pop3 logins and 40 imap while performance is a lot faster.
The previous system, giving us all the problems, was on a virtual server running Virtual Iron software. The hardware was the same on both.
Here's what I was seeing, that contributed to the problems causing 7000 angry customers to call us :)
[root@pop etc]# ps aux | grep pop3 | wc -l 740 [root@pop etc]# ps aux | grep imap | wc -l 450 [root@pop etc]#
May 29 11:42:19 pop dovecot: POP3(xxx): Time just moved backwards by 1 seconds. I'll sleep now until we're back in present. May 29 11:42:19 pop dovecot: POP3(xxx): Time just moved backwards by 1 seconds. I'll sleep now until we're back in present. May 29 11:42:31 pop dovecot: POP3(xxx): Time just moved backwards by 1 seconds. I'll sleep now until we're back in present. May 29 11:42:42 pop dovecot: POP3(xxx): Time just moved backwards by 1 seconds. I'll sleep now until we're back in present.
I was also getting postfix "backwards time" errors. I guess these errors were causing login sessions to stay up longer then they should have which backed up my server. I hope this helps someone out sooner as I had a feeling the time was causing the problems but mgt here didn't let me try to move it to another server until they exhausted all other options.
Thanks,
Paul