KVM in HA active/active + fault-tolerant configuration

[g.danti@assyoma.it]

Hi all,
I have a question about Linux KVM HA cluster.

I understand that in a HA setup I can live migrate virtual machine 
between host that shares the same storage (via various methods, eg: 
DRDB). This enable us to migrate the VMs based on hosts loads and 
performance.

ìMy current understanding is that, with this setup, an host crash will 
cause the VMs to be restarded on another host.

However, I wonder if there is a method to have a fully fault-tolerant 
HA configuration, where for "fully fault-tolerant" I means that an host 
crash (eg: power failures) will cause the VMs to be migrated to another 
hosts with no state change. In other word: it is possible to have an 
always-synchronized (both disk & memory) VM instance on another host, so 
that the migrated VM does not need to be restarted but only 
restored/unpaused? For disk data synchronization we can use shared 
storages (bypassing the problem) or something similar do DRDB, but what 
about memory?

Thank you,
regards.