I don't have an answer to your first question, we never set up our tape dirves in that manner. marianne's post indicated that the tape drives *can* be connected in Solaris Zone virtualization, see the Technote she linked to in her post above.
A media server may back itself up to any storage attached to it. Since you seem to have a path to the tape drives maped from your media servers to your master, then they are able to back up any NFS mount that is defined to them to the tape drives physically connected to the master server.
And that means that your third question is answered by what I just posted, I would think. It's confusing to me, too!
Now a bigger problem: you previously posted in another thread that you have 8 tape drives. A single Solaris server couldn't possibly stream data fast enough to all 8 tape drives at once to keep them from shoe-shining the tapes. Even though you have two virtual media servers that can also write to those tape drives, the way they are configured is likely slowing the backup data:
from the client --> across the network --> to the media server --> back across the network --> to the master server --> across the fiber channel path --> to the tape drives.
An ideal situation would be:
from the client --> across the network --> to the media server --> across the fiber channel path --> to the tape drives.
You likely have some very slow throughput to your tape drives, if any more than one or two are running backup at the same time. Few physical servers are capable of sending more than 2 or 3 streams of data fast enough to fiber channel connected tape drives. And my experience with Solaris is that it is far, FAR slower than a Linux or Windows based server when dealing with a lot of I/O across the various devices.
