In a SAN, you need a SAN SSO license for each MEdia server when each media server has access to a shared device. So, you count the number of Media servers in the SAN that access the VTL through the FC SAN. IT will give you the number of SAN SSO license you need. YOu then install SSO on each MEdia server. For Library Expansion Option, you count the MAx number of drives you are going to emulate using VTL. You remove 1 since 1 is always included with BE core. This will give you th enumbner of LEO licenses you will need (For ex : 4 drives max emulated, you need 3 LEOs).
YOu then installt he 3 LEO licences on each MEdia server (in other words, you intall the same LEO key multiple times. This is fine.
AS far as Local or Remote, it depends on the performance you expect. GOing direct through SAN to the VTL will be much faster than going thorugh LAN, but requires th extra BE Core license + SSO. In many cases, you can mix and match : The largest and most critical servers are backed up through the SAN (therefore require a Core BE licence + SSO) other servers are backed up through the LAN using the proper database agent or a simple Agent for Windows (AWS).
IF you have a large number of BE Core, it may soon become difficult to manage. YOu can then look inot adding a Central Admin Server licence (CASO).
CASO will enable you to centrally manage all BE core, deplying jobs from this central point to the remote "Managed Media servers" and getting back reports from them.
YOu could even do load balancing between MEdia servers to ensure the proper performance of your backup system
