[Dovecot] rc14 and rc15 performance issues
Hi,
I am stuck at rc13 because rc14 and rc15 have both failed to keep up with imap connections on my (slow old) system. I have the problem where if a lot of people check their email at once (like at the top of the hour) then my load goes way up and things slow to a crawl. My setup: Solaris 10 on an E220R, mbox format, imap and imaps only. I also use "login_process_per_connection = no". Any suggestions?
Jeff Earickson Colby College
On 2006-11-20 09:25:18 -0500, Jeff A. Earickson wrote:
I am stuck at rc13 because rc14 and rc15 have both failed to keep up with imap connections on my (slow old) system. I have the problem where if a lot of people check their email at once (like at the top of the hour) then my load goes way up and things slow to a crawl. My setup: Solaris 10 on an E220R, mbox format, imap and imaps only. I also use "login_process_per_connection = no". Any suggestions?
you should check where the time goes into: CPU bound, io bound? if it is IO bound. you might try maildir.
darix-- openSUSE - SUSE Linux is my linux openSUSE is good for you www.opensuse.org
On Mon, 2006-11-20 at 09:25 -0500, Jeff A. Earickson wrote:
Hi,
I am stuck at rc13 because rc14 and rc15 have both failed to keep up with imap connections on my (slow old) system. I have the problem where if a lot of people check their email at once (like at the top of the hour) then my load goes way up and things slow to a crawl. My setup: Solaris 10 on an E220R, mbox format, imap and imaps only. I also use "login_process_per_connection = no". Any suggestions?
Like Marcus asked, is it I/O load or CPU load? And if CPU, what process is using it? What passdb and userdb do you use? If you're not sure if it's imap process or something else doing it, you could eg. run with rc15's imap and everything else with rc13, or vice versa.
Anyway I don't see what could have caused anything to work slower..
On Mon, 20 Nov 2006, Timo Sirainen wrote:
Date: Mon, 20 Nov 2006 18:36:17 +0200 From: Timo Sirainen <tss@iki.fi> Reply-To: Dovecot Mailing List <dovecot@dovecot.org> To: Jeff A. Earickson <jaearick@colby.edu> Cc: dovecot@dovecot.org Subject: Re: [Dovecot] rc14 and rc15 performance issues
On Mon, 2006-11-20 at 09:25 -0500, Jeff A. Earickson wrote:
Hi,
I am stuck at rc13 because rc14 and rc15 have both failed to keep up with imap connections on my (slow old) system. I have the problem where if a lot of people check their email at once (like at the top of the hour) then my load goes way up and things slow to a crawl. My setup: Solaris 10 on an E220R, mbox format, imap and imaps only. I also use "login_process_per_connection = no". Any suggestions?
Like Marcus asked, is it I/O load or CPU load? And if CPU, what process is using it? What passdb and userdb do you use? If you're not sure if it's imap process or something else doing it, you could eg. run with rc15's imap and everything else with rc13, or vice versa.
Anyway I don't see what could have caused anything to work slower..
Because of screaming users, I didn't have a lot of time at analyze the situation. The cpu load climbed and climbed, to 40+ (uptime number), memory was really low, it may have been paging. passdb is passwd-file and userdb is passwd, nothing exotic here.
We have times like the top of the hour, and 11 AM especially, where everybody checks their email at once. This tends to spike the load. With rc13, it drops back quickly. With rc14/15 it goes up and stays there. Memory leak someplace?
Our IMAP server is seriously underpowered and needs to be replaced.
Jeff Earickson Colby College
Curtis Maloney wrote:
Jeff A. Earickson wrote:
Our IMAP server is seriously underpowered and needs to be replaced.
Just out of curiosity, how many users are we talking here?
Colby appears to have 1,871 students, about 220 faculty and I'm guessing 250 administrators/staff. So 2340 or so.
I sympathize with your situation, I've been there. We have "Chapel" for a half hour every day, and _maybe_ 5% of our students/users/staff go to chapel, so (and we have closer to 3000 users) we have at least 2x our peek usage not counting chapel during that time.
(and before I say this, I understand that your immediate problem is possibly a difference between rc13 and rc14/15 but I thought you might appreciate the knowledge of what we did in essentially the same situation as I imagine that even if the problem is solved this week by finding a memory leak its only a matter of time.)
We used to run UW IMAP on Solaris using mbox. When we did we did a few things which did a good job of acting as stopgates:
- We moved from using raid5 to raid 10. Based on some benchmarks I did recently on modern hardware which will soon be one of our dovecot cluster machines, raid 10 is about 3x as fast for block writes and 50% faster for block reads than raid 5.
- We added more ram. Which, if you are possibly swapping you should certainly do, but even if you aren't the more ram you have the less often you have to touch the disks due to cache.
- We added a 3rd mirror to our raid 10.
(then we moved to a linux box with 6g of ram and 22 1k fc disks for inboxes in raid 10 running uw imap)
Hmm, perhaps people would like to see the results of the benchmarks I ran on this list...
Ethan Sommer
--
Ethan Sommer Systems Administrator Gustavus Adolphus College 507-933-7042 sommere@gac.edu
We have roughly 3K users. Not all of them use webmail/IMAP, probably around half that number actually hit the dovecot server.
Jeff Earickson
On Tue, 21 Nov 2006, Curtis Maloney wrote:
Date: Tue, 21 Nov 2006 09:38:36 +1100 From: Curtis Maloney <cmaloney@cardgate.net> To: Jeff A. Earickson <jaearick@colby.edu> Cc: Dovecot Mailing List <dovecot@dovecot.org> Subject: Re: [Dovecot] rc14 and rc15 performance issues
Jeff A. Earickson wrote:
Our IMAP server is seriously underpowered and needs to be replaced.
Just out of curiosity, how many users are we talking here?
-- Curtis Maloney cmaloney@cardgate.net
participants (5)
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Curtis Maloney
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Ethan Sommer
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Jeff A. Earickson
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Marcus Rueckert
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Timo Sirainen