vSphere 5: HA Demonstration
I realize vCenter will initialed a migration of the VM however this will get the process halt. We have to kill the process and wait for a timeout in order to take over the VM again else no options will be available for control.
In conclusion, HA protects hosts failure and not device failure on host.
Troubleshooting virtual machines that loses disk access
Update 14 Nov 2011
What if you meet with a power outage? All hosts were shutdown? The answer is posted on Yellow Bricks.
Basically if it was not powered off gracefully it will be power on the VMs base on the protected list after the election process of electing a Master is completed.