What’s the need for separate network for storage why LAN cannot be used?

Question

i. SAN is generally more expensive but provides higher performance
ii. NAS uses TCP/IP for communication between hosts and the NAS server
iii. NAS requires additional hardware on a host: a host bus adapter for connectivity
iv. SAN uses proprietary protocols for communication between hosts and the SAN fabric

Answer 1

LAN hardware and operating systems are geared to user traffic, and LANs are tuned for a fast user response to messaging requests.

With a SAN, the storage units can be secured separately from the servers and totally apart from the user network enhancing storage access in data blocks (bulk data transfers), advantageous for server-less backups.