A bit of both? They were LVM mapped devices but hosted on external block storage. This particular setup was at RackSpace so each NFS server was a VM that mounted a block storage device which was shared over NFS and synced with DRBD.

Is the /dev/xvdb1 a shared device presented to each node from a SAN/NAS, or is it an LVM device on each node?

Gluster is definitely a good option to check out. I’m usually more of a cutting edge type person but in this case I had some experience with DRBD & Pacemaker so decided to go that route instead of Gluster, though I would like to play around with it some more (and probably will on future projects). It’s definitely a tricky situation with dual primary which is why the fencing/STONITH setup is so important, but so far I haven’t run into any issues with this config, knock on wood.

One other thing you might consider looking at is Gluster, which appears to provide a highly-available distributed and fault-tolerant file system with a much less complicated setup. Dual-primary DRBD would concern me a little, especially if it behaved anything like master-master MySQL does. Given storage is more your field than mine, would you consider giving Gluster a go?

Oops, I got busted. My original design called for using Heartbeat to manage the cluster (which is why it was indicated here) but ultimately I decided to use GFS2, Pacemaker, and a hardware load balancer for my NFS cluster (http://justinsilver.com/technology/linux/dual-primary-drbd-centos-6-gfs2-pacemaker/). The downside is that it requires some additional hardware ($$$) and configuration but does allow both nodes to be used at the same time.

Since I said I was going to use Heartbeat for the ha-cluster here I’ll update this post (as soon as I can) with the details of what that configuration would look like and give you a ping – thanks for reading!