What is the underlying reason for doing this?

Is the goal to improve the network throughput on the media server or do the clients have an actual need to be on four different vlans?

If you did it that way you would create a "virtual" media server entry for each ip.

The real challenge comes with the tape drives. Although the drives can be shared among the virtual media servers, with SSO, only one virtual media server can write to a specific tape drive at any one time.

Without going into too much detail you may have difficulty keeping all four tape drives running at full speed on one host. If they are not running at full speed the backup throughput performance will drop sharply.  

There may be better options if the goal is to just improve throughput.

-IPMP

-Ethernet Trunking.