[CentOS] About Memory mirroring

Greetings,

Was wondering if any software exists for mirroring memory across hosts
like what drbd does for disks.

I am somewhat aware of copying of a VM's memory when a live migration is done.

Another query, as I have not seen too many VM migrations, is that what
happens to the memory contents such as data yet to be written onto
disk, states etc happens when one of the RHCS cluster hosts which is
running  VM fail: does the cluster restart the machine?

An example perhaps would be suppose the VM is running a movie what
would the user's experience would be.

I tried it on cluster with ctdb. The movie simply restarted.

Any experiences?

-- 
Regards,

Rajagopal