What is a Storage Area Network (SAN)? SAN Defined | IBM

Computer memory and local storage resources might not provide enough storage, storage protection, multiple-user access, or speed and performance for enterprise applications. So, most organizations employ some form of a SAN in addition to network-attached storage (NAS) for improved efficiency and better data management.

Traditionally, only a limited number of storage devices could attach to a server, limiting a network’s storage capacity. But a SAN introduces networking flexibility enabling one server, or many heterogeneous servers across multiple data centers, to share a common storage utility. The SAN eliminates the traditional dedicated connection between a network file server and storage — and the concept that the server effectively owns and manages the storage devices — eliminating bandwidth bottlenecks. A SAN eliminates single points of failure to enhance storage reliability and availability.

A SAN is also optimal for disaster recovery (DR) because a network might include many storage devices, including disk, magnetic tape and optical storage. The storage utility might also be located far from the servers that it uses.