Excellent resources....

Clustered Filesystem with DRBD and GFS2 on CentOS 5.4

...a short walk-through of how to set up a filesystem, which replicates across two web nodes, and allows concurrent access from both nodes. This scenario is particularly useful, when you intend to load-balance or automatically fail-over two web nodes...

Clustered Filesystem with DRBD and OCFS2 on CentOS 5.5

...OCFS2 works very similar to GFS2, except that it doesn't use RedHat's Cluster Manager, but instead ships with O2CB, Oracle's own cluster manager. As far as the filesystem is concerned, it does the same thing.

I've been playing with both solutions in VirtualBox with a plan to roll out to ec2 and solve my cpu issues.

GFS won't be happening in EC2 as that requires multicast, I've played with IPSEC and GRE and the redhat clustering stuff just won't bind to the tunnel interfaces.

OCFS2 looks like it will work, I'll be testing on a micro-instance later but doesn't support SELINUX so I'll need to review my security config.

More posts no doubt as testing continues!