[Dovecot] Solaris/SSLonly/Lots of Users

Jeff A. Earickson jaearick at colby.edu
Wed Feb 21 17:45:56 UTC 2007

On Wed, 21 Feb 2007, Chris Wakelin wrote:

> Date: Wed, 21 Feb 2007 17:40:31 +0000
> From: Chris Wakelin <c.d.wakelin at reading.ac.uk>
> To: Steven F Siirila <sfs at tc.umn.edu>
> Cc: dovecot at dovecot.org
> Subject: Re: [Dovecot] Solaris/SSLonly/Lots of Users
> Steven F Siirila wrote:
>> Anyone running Dovecot on Solaris, requiring only SSL connections, and
>> servicing thousands of simultaneous users?  Our past attempts to do so
>> have failed due to dovecot-auth using up all 256 of its file descriptors.
>> I say 256 since we are limited to that by the 32-bit libraries.
>> We are looking at either compiling Dovecot in 64-bit and letting dovecot-auth
>> file descriptors accumulate (not ideal), or providing Timo with access to
>> one of our test servers so he can debug the problem.  However, I would
>> like to hear of anyone in the same boat first.  Thanks!
> You don't need it to be 64-bit, just change the ulimit/plimit parameters
> on the processes (try "man plimit"). You can change the default by
> editing /etc/system
> e.g.
> set rlim_fd_cur=2048
> set rlim_fd_max=2048
> to set the limit to 2048. We run "plimit -n 4096" on the dovecot master
> process shortly after it starts and typically have 1200 or so concurrent
> IMAP processes. Also look at "login_process_per_connection = no" in the
> Dovecot configuration; this will mean the number of imap-login processes
> is much reduced at the loss of a bit of security.

In my case (Solaris 10), I have the following set in my /etc/system.
This may be overkill/wrong:

* double file descriptor limits for dovecot
set rlim_fd_cur = 65536
set rlim_fd_max = 131072

But things work.

Jeff Earickson
Colby College

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