Quick Intro to the Difference Between SAN and NAS

At first glance NAS and SAN might seem almost identical, and in fact many times either will work in a given situation. After all, both NAS and SAN generally use RAID connected to a network, which then are backed up onto tape. However, there are differences -- important differences -- that can seriously affect the way your data is utilized. For a quick introduction to the technology, take a look at the diagrams below.

Wires and Protocols
Most people focus on the wires, but the difference in protocols is actually the most important factor. For instance, one common argument is that SCSI is faster than ethernet and is therefore better. Why? Mainly, people will say the TCP/IP overhead cuts the efficiency of data transfer. So a Gigabit Ethernet gives you throughputs of 600-800 Mbps rather than 1000Mbps.

But consider this: the next version of SCSI (due date ??) will double the speed; the next version of ethernet (available in beta now) will multiply the speed by a factor of 10. Which will be faster? Even with overhead? It's something to consider.

The Wires
--NAS uses TCP/IP Networks: Ethernet, FDDI, ATM (perhaps TCP/IP over Fibre Channel someday)
--SAN uses Fibre Channel

The Protocols
--NAS uses TCP/IP and NFS/CIFS/HTTP
--SAN uses Encapsulated SCSI