[Dovecot] distributed mdbox

[Jim Lawson]

On 03/22/2012 12:11 AM, Stan Hoeppner wrote:
> On 3/21/2012 12:04 PM, Timo Sirainen wrote:
>> The problem is most likely the same as with NFS: Server A caches data -> server B modifies data -> server A modifies data using stale cached state -> corruption. Glusterfs works with FUSE, and FUSE has quite similar problems as NFS.
>>
>> With director you guarantee that the same mailbox isn't accessed simultaneously by multiple servers, so this problem goes away.
> If using "real" shared storage i.e. an FC or iSCSI SAN LUN, you could
> use a true cluster file system such as OCFS or GFS.  Both will eliminate
> this problem, and without requiring Dovecot director.  And you'll get
> better performance than with Gluster, which, BTW, isn't really suitable
> as a transactional filesystem, was not designed for such a use case.

Speaking as an admin who has run Dovecot on top of GFS both with and
without the director, I would never go back to a cluster without the
director.  The cluster performs *so* much better when glocks can be
cached on a single node, and this can't happen if a single user has IMAP
processes on separate nodes.

No, you don't strictly need the director if you have GFS, but if you can
manage it, you'll be a lot happier.

Jim