[logicalstack]

CARP and similar systems require an active/passive configuration which we did not want since it needs at least twice as many hosts, half of which are not doing any work. We had similar issues with our former Git storage system based on DRDB (http://githubengineering.com/introducing-dgit/).

pfsync, lvs and etc uses multicast to share connection state which we also wanted to avoid.

[voltagex_]

Why do you want to avoid multicast?

[ctrlrsf]

You would need a large L2 network to support it, or you'd have to route it at L3, which is not trivial.