Chapter 12. Storage Area Networks

A storage area network (SAN) is a network of managed, shared, and distributed storage assetsa network of storage servers, if you will. You might infer that a SAN must have its own dedicated network, and for the most part, you would be correct, at least historically. As described in the Chapter 11, "Disk Subsystems," SANs are built with Fibre Channel switches and hubs, and the nodes are linked with either fiber-optic or coaxial cabling.

That storage network interfaces to a local area network (LAN) of servers and clients, where each server and client on the LAN connects to the SAN either through a file server or with a connection to the SAN itself. As Ethernet has gotten faster, and as the storage industry has found ways to permit hosts to transfer large amounts of data by offloading the processing required, there has been more and more interest in eliminating separate storage networks and unifying a whole networking enterprise. There's no hard-and-fast definition of what constitutes a SANonly that it achieves the desired aim of making storage available to clients.

Most SANs are built to network vast amounts of storage data. When you consider that a large EMC, Hitachi Data Systems, IBM, or Hewlett-Packard storage server can contain hundreds of terabytes of data stored on as many as a couple hundred disk drives and that many storage deployments network petabytes of data, SANs make a lot of sense. There's an enormous amount of money invested in storage (often it's more than 50% of the IT budget), and it's important to get the most out of that investment.

Note

For a more in-depth discussion of SANs, see Using Storage Area Networks Special Edition.

In an era when you can create a RAID array of more than a terabyte from three 400GB hard drives or purchase a network attached storage (NAS) appliance such as LaCie's Bigger Disk Extreme (1.8TB for $1,700), the time has come to consider applying the principles of storage area networking to your own servers and your own network. If you find yourself backing up computers at night in order to keep your LAN from being saturated by backup traffic, or if you find that your client systems have difficulty getting needed files from a central repositorylet alone finding them in the first placeyou are an ideal candidate for this technology.