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.
I am sorry but I do not share that view for incoming mail. The latency in getting the mail replicated probably is longer than it takes to do the actually delivery to the mail store.
DRBD works approximately like raid1 mirroring. Unless something breaks it shouldn't add much latency since the duplicate disk will run at approximately the same speed as the master.