Consider the following scenario:
– You have a Windows Server 2012 Hyper-V platform
– You virtualized windows server 2012 domain controllers : You have Windows Server 2012 domain controllers as virtual machines on this platform
– The host that holds the DC VM crashes (Power Outage) or an unplanned restart occurs.
– You start the hyper-V host and start the VM, or the VM is started in another Hyper-V host (cluster case)
– The DC VM may not start and the DC database may be corrupted
More explanation here