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