Ive read that when running svc 2008 as a guest on hyperv 2008 that the host should not be joined to the domain because on restart if the host it presents a chicken and egg problem. I have been reading about hyperv 2012 and its recommended that it should be part of the domain but nothing is mentioned about SBS 2011.
If I will be running SBS 2011 as a guest on hyperv server 2012 should the host be joined to the svc domain? Does the answer change if there will be another physical server which is also a dc and part of the sbs domain?
The issue of needing a domain controller to start Hyper-V is more problematic when you are running a Hyper-V cluster as it leverages failover clustering in windows which requires the domain to start the services. A standalone Hyper-V host joined to the domain would still be able to start, have an admin login with either cached creds or the local admin account and start the virtual DC. Hyper-V 2012 now has the ability to start the cluster without a DC available as well (but you still need a domain built first to build the cluster in the first place).
That being said, regardless of if you join your Hyper-V host to the domain, I would still recommend having a physical DC.