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

[Stan Hoeppner]

On 7/20/2011 1:27 PM, Matthew Macdonald-Wallace wrote:
> On Tue, 2011-07-12 at 07:03 +0100, Matthew Macdonald-Wallace wrote:
>> On Tue, 2011-07-12 at 00:21 -0500, Stan Hoeppner wrote:
>>> Are these virtual machines?  You didn't state so previously.  Running
>>> 2.6.18 as a VM guest on these machines may also be part of the incorrect
>>> load reporting problem.  If so, run the data collector daemon inside the
>>> hypervisor itself so you get actual load figures.  You'll never get
>>> accurate performance metrics for a whole box from a kernel/daemon inside
>>> a VM guest.
>>>
>>
>> Nope, all on the bare metal in our own datacentre.
>>
>> I'll let you know how the HT switchoff goes.
>>
>> M.
> 
> Hi all,
> 
> Just to let you all know that once we upgraded to Dovecot 1.2 (and
> enabled attribute caching on the NFS devices!) the loads settled down.

If you're running with NFS caching enabled in v1.x you need to read:

http://wiki.dovecot.org/NFS

> We've seen a drop in 15 minute load average from 12 to 2 and a drop in
> NFS I/O from 30K I/OPS to 3K I/OPS whilst continuing to serve the same
> number of queries - quite a difference!

Great.  Glad to see you're making some headway.

Worth noting, this is the first time in this thread that you've
mentioned your NFS load.  Up to now you mentioned only CPU and memory
consumption as problem areas.

> Thanks to all who helped,

The suggestion to upgrade to 1.2 was made very early on.  Which helped
more, v1.2 or enabling NFS caching?

Also, did you test any machines with hyper-threading disabled?  If so,
what effect did it have, if any?

-- 
Stan