[Dovecot] Outlook 2010 very slow when using IMAP - are there any tweaks?

Kaya Saman kayasaman at gmail.com
Tue Jul 3 13:51:34 EEST 2012

On Tue, Jul 3, 2012 at 11:37 AM, Charles Marcus
<CMarcus at media-brokers.com> wrote:
> On 2012-07-03 3:12 AM, Kaya Saman <kayasaman at gmail.com> wrote:
>> However this is a clean server with plenty of space left on the pool
>> allocated for mail and it's additionally using ZFS too.
> What OS? ZFS implementation/version? How is mail stored (maildir? mbox?)
> While I don't think this is your problem, just fyi, my understanding is that
> it is fairly easy to implement ZFS wrong (which would cause serious
> performance problems), and that the only decent ZFS implementation is Suns
> (ie, what ships with Nexenta), or the latest FreeBSDs...
> Also, my understanding is that ZFS isn't the snappiest of filesystems even
> when properly configured (you trade performance for data integrity).
> Personally, I'd recommend trying this on a traditional FS (XFS or Reiserfs
> for maildir) and see if that changes things.

FreeBSD 8.2 x64 using Maildir. ZFS is perfect no worries with that!!!
Additionally the system is on a VMware cluster which is also fine -
have checked all as diagnostics.

The usage here is minimal, and since I also use ZFS at home too with
quite a larger file system then at work (I know I know) and really
hammer the heck out of it there is no issue.

> On 2012-07-03 3:12 AM, Kaya Saman <kayasaman at gmail.com> wrote:
>> The point is that I am monitoring using nload as well as other things
>> and the maximum bandwidth being got with Outlook is a few Mbps burst,
>> average 50kbps; while with T-Bird I get way over 130Mbps?
> Congrats - there's your problem... now you need to find out *why* this is so
> slow... most likely a tcp dump analysis of a session is the only way - I
> think there are people here who could help you analyze one (but not me,
> sorry)...

Yeah, it seems to be M$ implementation of IMAP. I don't think that
there's anything anyone can do.... Outlook seems to wait after each
transmission (found using Wireshark).

> On 2012-07-03 3:41 AM, Kaya Saman <kayasaman at gmail.com> wrote:
>> The PST's seem to be stored on local hard disk too.
> 'Seem' to be? You need to make sure, because if they aren't that could
> definitely cause, or at least contribute to this kind of problem.

It is definitely stored locally!

> --
> Best regards,
> Charles



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