[Dovecot] Multiple locations, 2 servers - planning questions...

[Jan-Frode Myklebust]

On Mon, Feb 27, 2012 at 02:51:54PM -0600, list at airstreamcomm.net wrote:
>
>  You could also look at GPFS
> (http://www-03.ibm.com/systems/software/gpfs/), which is not open source
> but it's apparently rock solid and I believe supports multisite clustering.

GPFS supports different modes of clustering. I think the appropriate
solution here would be to deploy a single cluster spanning 3 sites (3. site
is needed for quorum node, two sites can't work because you can't protect
it from split brain). The simplest config would then be 3 nodes (but you
could have any number of nodes at each site):

	quorum node1 on site1 with a local disk (or local SAN-disk) as Network Shared Disk (NSD)
	quorum node2 on site2 with a local disk (or local SAN-disk) as Network Shared Disk (NSD)
	quorum node3 on site3

The filesystem would be replicated (over IP) between the disk on site1 and
site2.  Should one site go down, the other site would survive as long as
it could still see the quorum node on site3. After a site has been down,
one would need to sync up the NSDs (mmrestripefs) to re-establish the
replication of any blocks that has been changed while it was down.


   -jf