[Dovecot] Redundant shared mail store?

[Joshua Goodall]

Jasper Bryant-Greene wrote:
> Hi guys
> 
> I'm about to embark on a project replacing a legacy single mail server
> running proprietary software with a cluster of Dovecot servers. We
> clearly need a shared mail store for these servers, but we are not
happy
> with simply using a server running NFS as this becomes a single point
of
> failure.
> 
> What have other people used? AFAICT our options are:
> 
> 	* A shared block device (Fibre Channel, iSCSI, ATAoE etc)
running
> GFS
> or similar to allow multiple servers to access it concurrently
> 
> 	* Two or more NFS units, either with built-in support for
> replication
> of FS changes and failover, or with scripts for achieving this
> functionality
> 
> I prefer option 1, although it's expensive. What have other people
used?
> Do we have other options?

I recommend a pair of NetApp filers (e.g. 2 x 3020c) exporting NFS from
shared disk shelves in their high-availability mode.  This is a hybrid
of the two options, except a) it's a fully supported and stable NetApp
configuration, b) they're sharing disk storage, c) you're not hog-tied
to GFS, d) it's the best NFS implementation in the world (you can even
trust the fcntl locking), e) it's really fast, f) NetApp's onboard
snapshots and other funky software bits will make you wonder how you
lived without them, g) the HA actually works.

I have a six-digit userbase with mailboxes in this configuration.

JG