Network attached storage (NAS) and storage area network (SAN) are systems that expand storage capacity on a network. They achieve this goal in different ways.
- NAS devices are connected to a local area network (LAN) through the network router or a network switch. Typically, ethernet cables are used for the connection in the same way that computers on the network are connected.
SAN devices connect to a number of servers using fibre channel. Most SAN systems use the small computer system interface protocol. An add-on card must be installed in each computer that will be connected to a SAN device. - Any computer on the network can see a connected NAS device, and each computer recognizes it as a shared, external storage drive. Because the NAS system hides machine-dependent, low-level data management, files on a NAS device can be shared with most operating systems simultaneously.
A SAN is seen by a connected server as a local drive. Since the SAN serves data only as raw disk blocks, the server itself must provide file management. - A NAS device can make files available to any computer on a network. Additional NAS devices can be added to the network to expand storage space, and the devices can work together to appear as a single, shared network drive.
A SAN provides storage space that can be shifted from one server to the next as the needs of each server change. Any capacity not being used by one server can simply be allotted to another. - NAS devices can be exposed on a wide area network such as the internet, making it possible to install a NAS system anywhere outside a home or office while still having shared access to its files.
According to the NAS-SAN website, the fibre channel used in a SAN has a maximum distance of 10 km. While this can provide shared storage between nearby offices and protection against some disasters, it limits the available locations where a SAN may be placed.
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