Edward Carraro put forth on 9/22/2010 10:03 PM:
We have a few dovecot servers all pointing to the same mail location (an NFS mount on a NAS drive).
This could lead to a possible bottleneck eventually and we were wondering if it's possible to have dovecot direct x number of users to one message store location while others get their mail on a different mount?
There are better ways to solve a storage bottleneck than trying to split user mailboxes across different storage back ends at the IMAP server (application) level. The most obvious is tweaking, upgrading, or wholesale replacing the storage infrastructure, not just slapping another NAS box on the network and splitting users. Doing what you are asking is a bandaid, not a good permanent solution, IMO. If you're going to add another NAS box, get a decent unit that is sufficiently expandable (disks and ports) and just migrate the entire mail store to it. For that matter, if your skill set is up to it, you could build your own Linux NFS server better and cheaper.
Could you give us more details as to why you believe you have a storage bottleneck looming? Are you unable to add disks to the current NAS box to increase spindle performance and total space? Given it's 2010, I'm assuming your NAS device has at least 2 GigE ports and you are doing link aggregation/port bonding with the quality managed switch it's connected too.
That should give you ~200 MB/s full duplex bandwidth and decent packet latency, which is more than sufficient for a half dozen or more dovecot cluster servers and a couple thousand users--assuming the NAS device isn't a piece of junk.
So exactly where is this looming bottleneck?
-- Stan