SAN, called Storage Area Network,or Network behind servers, is specialized, high speed network attaching servers and storage devices.A SAN allows "any to any" connection across the network, using interconnect elements such as routers, gateways, hubs and swithes. it eliminates the traditional dedicated connection between a server and storage, and concept that the server effectively "owns and manages" the storage devices. It also eliminates any restriction to amount of data that a server can access, currently limited by the number of storage devices, which can be
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. And, the storage utility may be located far from the servers which use it.
A SAN differs from traditional networks, because it is constructed from
storage interfaces. SAN solutions utilize a dedicated network behind the
servers, based primarily (though, not necessarily) on Fibre Channel
architecture. Fibre Channel provides a highly scalable bandwidth over long
distances, and with the ability to provide full redundancy, including switched,
parallel data paths to deliver high availability and high performance.
Therefore, a SAN can bypass traditional network bottlenecks. It supports
direct, high speed transfers between servers and storage devices in the
following ways:
• Server to storage. This is the traditional method of interaction with
storage devices. The SAN advantage is that the same storage device may
be accessed serially or concurrently by multiple servers.
• Server to server. This is high speed, high volume communications
between servers.
• Storage to storage. For example, a disk array could backup its data
direct to tape across the SAN, without processor intervention. Or, a device
could be mirrored remotely across the SAN.
A SAN changes the server centric model of the typical open systems IT
infrastructure, replacing it with a data centric infrastructure.
