On 03/22/2012 12:11 AM, Stan Hoeppner 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
On 3/21/2012 12:04 PM, Timo Sirainen wrote: 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