Open HA Cluster has now made available an agent for xVM Server x86-64 guest domains. The nice part of the HA-xVM Server x86-64 agent is that we're only being holistic by gluing projects together in OpenSolaris, Open HA Cluster (based on Solaris Cluster), + xVM (based on Xen). The HA-xVM Server x86-64 agent simply aims to mitigate against the failure of a physical server that may be hosting several heterogeneous xVM Server x86-64 guest domains
Actually, it's a very simple idea to visualise. The HA-xVM Server x86-64 agent monitors guest domains as well as the physical server those domains are running on. If either fails, then the HA-xVM Server x86-64 agent fails over the domain to another x86-64 xVM node.
If you're familiar with the term “live migration,” then you may already know that live migration is not high availability. Suppose you have just lost the server hosting your domain; you can't now live migrate from that server. If, on the other hand, you live migrated 5 minutes before the server failed [read hindsight], then you just got lucky. If the server fails before or during live migration, then you can only restart that domain on another node. Essentially, the HA-xVM Server x86-64 agent detects and reacts to these scenarios.
Anyway, if you're interested, check out Open Solaris HA-xVM Project, where you'll find an extensive HA-xVM Server x86-64 cheat sheet and an installable package of the agent to try out.
Solaris Cluster Engineering