Backing up volumes in a Windows Failover Cluster

What I do.
install NB on the two physical servers, with the client name being the physical servers.

I setup a policy to backup the physical servers: (I call this one physical_clusters)
C:\
System State/Shadow copy (depending on the OS version)

I then setup a policy(s) to get the other stuff.
Logging into one of physical servers I go to Cluster Administrator.
Under Groups I look at the virtual names and see what resources each of them owns.
I then setup a policy to get the resources.

CLSTR_Vserver1
M:\
N:\

CLSTR_Vserver2
P:\
R:\

Now I know I get the items from the physical that I need
and I get the resources no matter what physical server they are currently on.
(NOTE:  if you log into a Vserver and look at the BAR you will NOT see the Vserver name - that is fine.  It works just fine so long as NB is installed on the physical servers)