Best practices: Virtual Active Directory Domain Controllers

Here's a number of best practices for virtual domain controllers:

1. Never, ever snapshot, never pause, and never clone via vmware client
2. Educate yourself on your backup solution and it's AD backup capabilities
3. Time Sync, is still very important.  Insure your host is sync'd or setup external time source
4. vmtools client, if stopped/crashed can cause time issues  
5. Make sure you can restore, not just backup.  Backups are useless if you can't restore.  The right backup solution will auto-verify the integrity 
6. Anti-affinity, make sure your DC's don't end up on the same host.