[Dovecot] POP3 vs. IMAP Load/Memory usage in Dovecot 1.0.15

[Matthew Macdonald-Wallace]

On Mon, 2011-07-11 at 13:47 -0500, Stan Hoeppner wrote:
> On 7/11/2011 11:22 AM, lists at truthisfreedom.org.uk wrote:
> 
> > They're showing as between 20 and 24 for the POP3 servers and 1.4 for
> > the IMAP servers.
> 
> FULL STOP.  Oh my lordy.  Something is ridiculously wrong here.  You
> have 12 physical cores with only ~600 simultaneous pop connections.
> That's only 50 per core.  Even if those are the 'lowly' 2.4GHz 5645
> chips each core should be able to handle a couple hundred pop
> connections.  If you were truly hitting an actual load of 20-24, a
> single one of those boxes would be bringing your NetApp to its knees
> (assuming GbE) due to the amount of IO that would be taking place with
> the CPUs this busy.

Good, so my assumption that something was wrong was correct and as the
NetApp isn't on its knees... 

> > So a kernel update is more than sensible...
> 
> Disable HT regardless of kernel upgrading.  See if it helps the load
> issue with the current kernel.  Then go ahead and upgrade the kernel.
> If the CentOS repos don't have anything in the 2.6.3x series grab:
> http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.39.3.tar.bz2
> 
> and roll your own.  Though I'd guess since you're a CentOS user you
> probably don't have any experience rolling kernels.

LOL. I'm not a fan of Centos but it's what we've got to play with here -
We'll be running Debian (or possibly even Gentoo if I have my way...) on
the next load of servers and custom kernels aren't an issue.

/me misses stage one gentoo installs... :(

> Now, considering you're running a many years old version of Dovecot,
> which is no longer officially supported, you really need to upgrade.
> Safe bet is to grab the latest 1.2.x RPM you can get.

We've built our own RPMS for 1.2 - we're upgrading these servers
tomorrow... :)

Kind regards,

Matt