On 3.1.2012, at 16.54, Mikko Lampikoski wrote:
I got Dual Core Intel Xeon CPU 3.00GHz, over 1000 mailbox and almost 1 dovecot login / second (peak time). Server stats says that load is continually over 2 and cpu usage is 60%. top says that imap is making this load.
You mean an actual "imap" process? Or more than one imap processes? Or something else, e.g. "imap-login" process? If there's one long running IMAP process eating CPU, it might have simply gone to an infinite loop, and upgrading could help.
virtual users are in mysql database and mysqld is running on another server (this server is ok).
Do I need better CPU or is there something going on that I do not understand?
Your CPU usage should probably be closer to 0%.
login_process_size: 128 login_processes_count: 10 login_max_processes_count: 2048
Switching to http://wiki2.dovecot.org/LoginProcess#High-performance_mode may be helpful.
mail_nfs_storage: yes
Do you have more than one Dovecot server? This setting doesn't anyway work reliably. If you've only one server accessing mails, you can set this to "no".