Hello Jack

Setting up imapproxy on a third machine greatly improve performances on my mailhub which doesn't refuse connexions anymore.

Thanks a lot for your help !

Frank

Jack Stewart wrote:

Frank Bonnet wrote:

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Timo Sirainen wrote:

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On Thu, 2009-01-15 at 16:25 +0100, Frank Bonnet wrote:

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I had to increase the max_mail_processes to 8192 to have a functionnal IMAP server with normal clients AND squirrelmail clients

8192 sounds enormous to me , any infos welcome !

How many imap processes have you running typically?

Hi,

I don't know if this will help or not - I'm taking my comments offline because it isn't clear if they are related to your core problem. Also, they seem to be specific to high usage servers/people.

We're not 1.1.8 yet but I've spent a reasonable amount of time tweaking the Linux side.

We run at about ~1300 processes per server.

Squirrelmail does a login/logout on every single page that is clicked. So I've found that running an imap proxy (such as the one at imapproxy.org really helps). It creates some additional connections but they get re-used pretty frequently.

If 1.1.8 isn't logging out quickly, or not cleanly shutting down the connection, or something similar, that could explain additional connections. What does netstat -an show? On some O/S's the process will disappear from ps but not be fully released until the socket/connection disappears (in this case tcp). If you have a bunch of WAIT/FIN_WAIT's something like this seems pretty likely.

I've found that going through localhost allows you to bypass TLS while still enforcing TLS for non-localhost connections. It's pretty nice for overhead/connect speed. Also, an imap proxy may need a non-encrypted connection.

Besides the dovecot max_ ... settings, in our system you need to tweak limits.conf and bump up the limits via the ulimit command in the dovecot init script. Open file descriptors and process limits seem to be the main settings.

After this, you get into kernel tuning such as inotify settings.

Let me know if you have any questions. If some of this helps, we might want to feed it back into the list.

---Jack