KVM Hosting: How to efficiently replicate guests
I wouldn't mess around with local storage, and set up a cluster with shared instead. oVirt and RHEV provide VM HA and load balancing out of the box, all you need is to set the VMs up, and if ahost goes down, the VMs that went down with it will automatically be started on another host.
For storage you can get a proper SAN, but if the budget is tight a RHEL box exporting iSCSI or NFS will do.
This iSCSI or NFS backend can easily be replicated, backed up and generally kept safe