Christopher Chan wrote:
No, mail spools/queues do not need replication. Stuff in the queue are usually deleted in a second and such dynamic change is not worth replicating. If you do put the queue on a distributed filesystem, in most cases you cannot have more than one instance running save for sendmail.
I think your statement here is flawed, in that if there is even a single bit of the process you dont replicate - you've already lost the HA game.
Besides, as John already pointed out, emails in the spools can hang around for days. I believe most MTA's only discard completely after 7days of non delivery.
the OP is taking about DRBD in a primary-> secondary setup, in which case, there wont be a clustered filesystem on the block device, and there will only really be one instance of the real app running.