we use netapp san for most of out storage. There are some host out there who use local disk as well.What is most efficient way to find out which server is using SAN. Does SAN management tool offer any such functionality?
You could use your zoning (SAN Access-control Lists) to see which servers are PERMITTED to talk on the SAN to other devices, but that ignores the possibility of asking for storage that never gets accurately used. That's like looking at a map to see what roads exist, and which roads may be driven on, but doesn't show you which are actually driven on.
You could also watch the fibrechannel transactions to see what exchanges happen, and who is talking to whom (in the RX_ID and OX_ID of the fibrechannel). That's what solutions such as Virtual Instruments VirtualWisdom do: by examining every single exchange, walking a Finite State Machine for each, and summarizing what happened at 8G speed for a bunch of fibre links. It's not free, but it tends to be accurate when you're interested in latency and performance of storage targets under demand/load, and whether some servers are never, ever, actually using SAN.