In perusing the Microsoft Hyper-V forums this weekend, I ran across Hyper-V/domain controller questions from users that had a variety of answer… not all correct.  The original question was whether or not the Hyper-V role could or should be installed on a domain controller.  In general, it’s recommended to avoid installing other server roles on a Hyper-V host, including the domain controller role.  However, it has become commonplace to virtualize most – if not all – domain controllers.  Of course, there are some precautions that need to be taken:

• At this point, never use the snapshot feature with a domain controller.  Recovering from a snapshot can corrupt AD beyond repair.  Rumor has it that the next version of Windows will not have this issue, but that’s still months away.  Always use system state backups for recovery.
• A best practice is to make sure that the virtual hosts housing domain controllers are on UPSs.
• Disable the write cache for servers hosting Active Directory components.

If you take reasonable precautions and follow Microsoft guidance, there’s no reason to avoid virtualization your domain controllers under Hyper-V.