Storage Area Network

A network designed to attach computer storage devices such as disk array controllers and tape libraries to servers. SANs are commonly used in enterprise storage.

There are two variations of SANs:

A network whose primary purpose is the transfer of data between computer systems and storage elements. A SAN consists of a communication infrastructure, which provides physical connections, and a management layer, which organizes the connections, storage elements, and computer systems so that data transfer is secure and robust. The term SAN is usually (but not necessarily) identified with block I/O services rather than file access services.

A storage system consisting of storage elements, storage devices, computer systems, and/or appliances, plus all control software, communicating over a network.

Sharing storage usually simplifies storage administration and adds flexibility since cables and storage devices do not have to be physically moved to move storage from one server to another. Note, though, that with the exception of SAN file systems and clustered computing, SAN storage is still a one-to-one relationship. That is, each device (or Logical Unit Number (LUN)) on the SAN is "owned" by a single computer (or initiator). In contrast, Network Attached Storage (NAS) allows many computers to access the same set of files over a network. It is now possible to combine the SAN and NAS using a NAS head.

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