Microsoft introduced a feature in Windows Server 2012 which enables snapshots to be reverted on Active Directory Domain Controllers without corrupting the Active Directory. This feature called VM-Generation ID also allows cloning of Active Directory running on virtual machines.
VMware vSphere 5.1 does support this feature since its release but I have not read a lot of information on it. Only recently VMware wrote a blogposting titled Windows Server 2012 VM-Generation ID Support in vSphere about the support.
VM-Generation ID functionality requires the hypervisor vendor to create the virtual machine identifier and expose it to the guest. VMware has provided this functionality in the following releases of vSphere
- VMware vSphere 5.0 Update 2 (vCenter Server and ESXi must both be at 5.0 Update 2)
- VMware vSphere 5.1 (ESXi must be at least 5.0 Update 2
This VMware document titled Testing the New Windows Server 2012 GenerationID, DC Cloning and DC Safeguards Features on vSphere has some very good information on the process on cloning a Windows Server 2012 Domain Controller. The PDF has lots of screendumps to explain.
Matt Liebowitz wrote a nice posting about cloning a Windows Server 2012 domain controller. Read the post here.
Microsoft described the process of cloning in a blogpost titled
Safely Cloning an Active Directory Domain Controller with Windows Server 2012 – Step-by-Step