A Storage area network, or SAN, is a high-speed network of storage devices that also connects those storage devices with servers. It provides block-level storage that can be accessed by the applications running on any networked servers. SAN storage devices can include tape libraries, and, more commonly, disk-based devices, like RAID hardware.
A SAN must be highly available. A good SAN implementation will have built-in protection against just about any kind of failure imaginable. This means that not only must the links and switches composing the SAN infrastructure be able to survive component failures, but the storage devices, their interfaces to the SAN, and the computers themselves must all have built-in strategies for surviving and recovering from failures as well.
A good SAN delivers both high data transfer rates and low I/O request latency. Ideally, the SAN’s performance must be able to grow as the organization’s information storage and processing needs grow
A SAN that scales can provide a boost in performance with extra applications by separating high-volume I/O traffic from client/server message traffic.
Any well-managed enterprise will do a cost-benefit analysis before deciding to implement storage networking. The results of such an analysis will almost certainly indicate that the biggest payback comes from using a SAN to connect the enterprise’s most important data to the computers that run its most critical applications.