Network Attached Storage (NAS) is a dedicated file server optimized to serve just files. Moreover, NSA is independent and shareable storage system and is connected to the network infrastructure through TCP/IP and remote NFS protocols and wires such as Ethernet, FDDI, ATM, HTTP, etc. Furthermore, in NAS architecture, you can add more storages without disrupting the network systems.
Whereas a storage area network (SAN) is a dedicated high performance network used to move data across different servers and storage systems. Moreover, it has separate and dedicated network used to avoid traffic conflict between clients and servers. Additionally, it is developed via fiber channel connections over iSCSI and FCoE protocols.
A SAN handles data via disk block numbers and it transfers raw disk blocks. Whereas NAS handles data by fine name and byte offsets and, as opposed to SAN, transfers file data and file meta-data. Another crucial distinction between SAN and NAS storage systems is the way backups are taken. In SAN storage, backups require a block-by-block copy. Whereas in NAS storage, backups are done one files not blocks.