The hypervisor must support VM-GenerationID. Besides protecting Active Directory from unintentional roll-back, these new safeguards and VM-Generation ID allow administrators to safely clone Windows Server 2012 domain controllers. When properly prepared, a Windows Server 2012 domain controller may be used as a source for new domain controllers. Not only does this eliminate the additional tasks of preparing a base virtual machine for becoming a domain controller, it reduces the time required for replication of a new copy of the Active Directory database.
VMware vSphere 5.1 (ESXi must be at least 5.0 Update 2) has provided this functionality, but hot cloning is NOT supported ref : VMware KB: Hot-cloning of Windows Server 2012 Domain Controllers is not supported