What is a Storage Area Network?
The Storage Network Industry Association (SNIA) defines the SAN as 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
Put in simple terms, a SAN is a specialized, high-speed network attaching
servers and storage devices and, for this reason, It is sometimes referred to as
“the network behind the servers.” A SAN allows “any-to-any” connection across
the network, using interconnect elements such as routers, gateways, hubs,
switches and directors. It eliminates the traditional dedicated connection
between a server and storage, and the concept that the server effectively “owns
and manages” the storage devices. It also eliminates any restriction to the
amount of data that a server can access, currently limited by the number of
storage devices attached to the individual server. Instead, a SAN introduces the
flexibility of networking to enable one server or many heterogeneous servers to
share a common storage utility, which may comprise many storage devices,
including disk, tape, and optical storage. Additionally, the storage utility may be
located far from the servers that use it.
The SAN can be viewed as an extension to the storage bus concept, which
enables storage devices and servers to be interconnected using similar elements
as in local area networks (LANs) and wide area networks (WANs): Routers,
hubs, switches, directors, and gateways. A SAN can be shared between servers
and/or dedicated to one server. It can be local, or can be extended over
geographical distances