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

[Stan Hoeppner]

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.

> 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.

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.

>> It may have been.  I'll know when you post your load numbers from those
>> top secret graphs. ;)
> 
> LOL, see above.
> 
> Thanks again,

You're welcome.  Your problem isn't solved yet, but it soon will be. :)

-- 
Stan