4gb of RAM is too low for Zimbra with 250 users

[borispr]

Centos 5 32bit and Zimbra 5.0.10
Major amount of users connected via imap. Everything was fine until the amount of users grown up. Right now Thunderbird has connection problems (timeout), free gives result:
total used free shared buffers cached
Mem: 3368328 3233316 135012 0 150348 1115612

When imap users have connection problem http users works without problem. When I do zmcontrol stop zmcontrol start it's about 600 mb of free memory which then decreases to 100 mb during imap users activity.
Seems the narrow place is imap service.

BTW ms exchange with such amount of users on a similar hardware works without problems.

[uxbod]

And the question is ? How large are peoples mailboxes what is the split between IMAP and WebClient ? Any additional software installed ? Any changes with respect to SpamAssassin on the default install ?

[borispr]

Originally Posted by uxbod

And the question is ? How large are peoples mailboxes what is the split between IMAP and WebClient ? Any additional software installed ? Any changes with respect to SpamAssassin on the default install ?

No question, just to inform.
90% uses imap, the default maximum mailbox size is 500 mb, about 10 users have 1-2-3 gb
No additional software, SA default settings, about 20000-30000 incoming mails per day

[borispr]

what imap server Zimbra is using?

[drhughes]

I find that vmstat is a better tool for determining the overall system performance. Memory issues can be tricky to track down. Your IMAP issue might be something such as file I/O slowing you down. This is where vmstat is a handy tool.

Correct me if I'm wrong, but using free will always show your system having little RAM free. Linux will use all available RAM for activities such has file system caching.

[dijichi2]

actually your memory stats show good free memory - the last number crudely represents your actual free memory, which is a third of your available. Also you're only showing having actually 3.2gb memory in total, where's the other 0.8gb gone?

your problem is more likely to be number of imap threads available or some kernel parameter related to max open threads/connection/sockets/processes. i would have thought you'll find there are quite a few people running 400+ users on your sort of hardware without problem.

[Vladimir]

Originally Posted by dijichi2

Also you're only showing having actually 3.2gb memory in total, where's the other 0.8gb gone?

32bit OS memory addressing issues?

[borispr]

Originally Posted by dijichi2

actually your memory stats show good free memory - the last number crudely represents your actual free memory, which is a third of your available. Also you're only showing having actually 3.2gb memory in total, where's the other 0.8gb gone?

32 bit CentOS without PAE

Originally Posted by dijichi2

your problem is more likely to be number of imap threads available or some kernel parameter related to max open threads/connection/sockets/processes. i would have thought you'll find there are quite a few people running 400+ users on your sort of hardware without problem.

I have found in variables "zimbraImapNumThreads: 200"
Might this is a reason. I have changed it to 400.

[iway]

Does it work for you now?

[borispr]

Yes, it helped.
As I understand web users are also use this imap sockets. Total amount (web+imap) were more than 200. After increasing this value I have no problem.