Storage Area Network Defined - IBM TotalStorage DS300 Best Practices Manual

1.2 Storage Area Network defined

The Storage Network Industry Association (SNIA) defines 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.
A SAN can also be a storage system consisting of storage elements, storage
devices, computer systems, and/or appliances, plus all control software,
communicating over a network.
Note: The SNIA definition specifically does not identify the term SAN with
Fibre Channel technology. When the term SAN is used in connection with
Fibre Channel technology, use of a qualified phrase such as
SAN
is encouraged. According to this definition, an Ethernet-based network
whose primary purpose is to provide access to storage elements would be
considered a SAN. SANs are sometimes also used for system interconnection
in clusters.
A SAN is a specialized, high-speed network attaching servers and storage
devices. It is sometimes called "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, 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 that use it.
The SAN can be viewed as an extension to the storage bus concept that 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.
Figure 1-1 on page 6 shows a tiered overview of a Storage Area Network
connecting multiple servers to multiple storage system.
Chapter 1. Storage Area Networks (SAN) overview
Fibre Channel
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