Storage Area Networks

As more business processes are computerized, enterprises are storing exact copies of all of their data at remote data centers and storage areas networks (SANs). A SAN is a network designed for backup and disk mirroring of large databases. These networks include those used for vital functions such as inventory, accounts receivable, order entry and accounts payable. Disk mirroring is the process of simultaneously writing data to backup and primary servers. SANs provide data restoral in the event of disasters or computer failures. They are located at the same site as the primary servers or at other locations in the metro area or across the country.

A data center is a centralized location for corporate data with special environmental controls such as air conditioning, fire alarms, and duplicate power sources. It also has special security provisions regarding who is allowed to enter the center. Data centers can support multiple enterprise sites. Some organizations hire outside organizations to manage their data center either at their site or at a remote site.

Enormous speed is required to transport the massive amounts of data between corporate sites and SANs and/or data centers. In some cases, data centers act as backups to each other. Fibre channel is a standard for high-speed connections at between 133 megabits per second and 4 gigabits per second between servers and storage devices. Fibre channel is used as a local physical channel within the data center. Because there are many devices in a SAN, SANs use either hubs or switches to distribute data to devices. Hubs provide a common path between devices, and switches establish dedicated paths. Fibre channel data is transmitted directly to devices' input/output interfaces. Fibre channel operates over most network protocols.

Because of the speed and reliability requirements, organizations typically use Ethernet VPNs, SONET, or leased fiber with an individual wavelength. Individual wavelengths have distance limitations of hundreds of kilometers but are less costly than SONET. Wavelengths are sent to data centers, customers, or SANs at speeds of 1.5 gigabits, 2.5 gigabits or 10 gigabits per second over one pair of fiber.