[contingencies]

DRBD? http://drbd.org/

[aphyr]

Same limitations as any asynchronously replicated system; if both nodes diverge during a partition, you'll probably have to drop one's writes.

http://aphyr.com/posts/287-asynchronous-replication-with-fai...

[contingencies]

Right. By operating at the block level it's a little more portable than most of the solutions discussed, though. Worth people's consideration, IMHO.

[aphyr]

I'm inclined to think just the opposite. It's often possible to recover divergent data structures logically. Good luck doing that on an arbitrary block store.

[contingencies]

My impression is that most DRBD setups are such that the backing volume is marked to recall which node last had 'master' (ie. write capacity), thus avoids this issue. However, to achieve this reliably it needs out of band STONITH (shoot-the-other-node-in-the-head), eg. IPMI.