[Dovecot] Performance question
I now have Dovecot in production and things are apparently trouble-free. The one known problem is that initial client inbox load can take 30 seconds - 2 minutes. For instance: 'I got fed up waiting and went and got coffee'...this with a 3MB mbox inbox...and my mail server is a substantial machine consuming 25% CPU just for this person's IMAP session. I realize that a certain amount of performance piggishness is inevitable with large mbox inboxes (the prize goes to the user with a 500MB inbox). Eventually, I plan to move to maildir format, but for now I'm here. Also, we have legacy requirement for procmail, so I can't currently use deliver.
Questions: the problem?
- Any tuning I can do to improve this?
- Any metrics, troubleshooting I should be doing to better characterize
--
Stewart Dean, Unix System Admin, Henderson Computer Resources
Center of Bard College, Annandale-on-Hudson, New York 12504
sdean@bard.edu voice: 845-758-7475, fax: 845-758-7035
- Stewart Dean <sdean@bard.edu>:
I now have Dovecot in production and things are apparently trouble-free. The one known problem is that initial client inbox load can take 30 seconds - 2 minutes. For instance:
Initial? Initial after what? I guess the index is being rebuilt, cold that be?
'I got fed up waiting and went and got coffee'...this with a 3MB mbox inbox...and my mail server is a substantial machine consuming 25% CPU just for this person's IMAP session.
Normal.
I realize that a certain amount of performance piggishness is inevitable with large mbox inboxes (the prize goes to the user with a 500MB inbox).
Eventually, I plan to move to maildir format, but for now I'm here. Also, we have legacy requirement for procmail, so I can't currently use deliver.Questions:
- Any tuning I can do to improve this?
Use deliver to rebuild the index wehenever a mail is delivered.
-- Ralf Hildebrandt (Ralf.Hildebrandt@charite.de) plonk@charite.de Postfix - Einrichtung, Betrieb und Wartung Tel. +49 (0)30-450 570-155 http://www.arschkrebs.de "The percentage of users running Windows NT Workstation 4.0 whose PCs stopped working more than once a month was less than half that of Windows 95 users."-- microsoft.com/ntworkstation/overview/Reliability/Highest.asp
On 19.7.2007, at 18.23, Stewart Dean wrote:
I now have Dovecot in production and things are apparently trouble- free. The one known problem is that initial client inbox load can
take 30 seconds - 2 minutes. For instance: 'I got fed up waiting and went and got coffee'...this with a 3MB
mbox inbox...and my mail server is a substantial machine consuming
25% CPU just for this person's IMAP session.
That sounds too much. Dovecot should take about the same time as UW- IMAP when initially opening the mailboxes.
- Any tuning I can do to improve this?
http://wiki.dovecot.org/PerformanceTuning has some suggestions.
- Any metrics, troubleshooting I should be doing to better
characterize the problem?
Can you easily reproduce this with any mbox file that's a few
megabytes large? Does deleting Dovecot's indexes and immediately
reopening the mailbox take as long? So does disk I/O have anything to
do with the wait, or is it just CPU?
participants (3)
-
Ralf Hildebrandt
-
Stewart Dean
-
Timo Sirainen