We're virtualized using ESXi. Every night we use ghettovcb to back up the vmdk's onto a remote NFS share. We know all about the dangers of virtualized DC's and take extra measures to never revert a snapshot on a DC, we also have DC's at each of our five remote facilities plus two at our HQ facility. The AD domain operates at a 2012 functional level.
In the past, with our 2003 DC's at a 2000 mixed functional level we would take a day old copy of a DC, put it on a private isolated network, and use it for tests and simulations. We've done it many times, simulating Exchange upgrades, SQL upgrades, Shoretel upgrades, etc.
Fast forward to today when we were trying to simulate a Sharepoint upgrade. We pulled the same trick with our 2012 DC, mounting a backup copy from the NFS share in an isolated environment. Problem is that AD never seemed to start. I've spent the better part of the afternoon googling but generally only find the standard "never virtualize your DC's" stuff rather than any solid advice on replicating your AD environment for testing. Any help is greatly appreciated--GD