[Dovecot] Virtual Servers

[Daniel L. Miller]

On 6/27/2011 6:06 PM, Noel Butler wrote:
> I hope this is a lightly used server and does not do any real level of
> mail traffic else you'll soon regret running in any VM :)
Just all the mailing lists I subscribe to :)

>>
>> means NFS.  My initial testing shows NFS results in a dramatically
>> reduced performance for Dovecot.  Given that this NFS access is going to
>
> Hrmmm, something amiss somewhere then, I'd put it down to the VM, many
> people on this list use NFS
> and have no problems.
>
Well - the wiki tells me, "Both the mmap_disable and indexing to NFS 
will result in a notable performance hit."
> Though you have not mentioned what version you run, on 1.2.x using:
>
> mmap_disable = yes
> mail_nfs_storage = yes
> mail_nfs_index = yes
Why do people insist on specifics :) ?  At the moment, 2.0.13.

Something still a bit unclear - cue Timo interjection here.  The 
parameters listed for nfs installations (mmap_disable, 
doctlock_use_excl, mail_nfs_storage, mail_nfs_index) - are they 
necessary for data integrity, and/or do they compensate for NFS latency 
and improve performance?  My confusion stems from the unusual? condition 
where the mail store is NFS based - but is otherwise dedicated to the 
single Dovecot instance, so simultaneous writes & locking *shouldn't* be 
a concern.

Particularly as I'm using mdbox, local index storage seems inappropriate 
(as I don't want any critical data stored within a virtual image).
-- 
Daniel