The SAN Era Takes Shape

Computer Technology Review,  May, 2000  by Fred Moore

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The era of Storage Area Networks (SANs) has started to take shape. A SAN is a dedicated network that connects all the servers and clients to a shared pool of storage devices. The pool consists of servers, external storage devices, hubs and switches, along with network and storage management tools. The SAN concept is being fueled primarily by advances in Fibre Channel, but can be constructed from SCSI, SSA, ESCON, and FICON I/O interfaces.

In a Fibre Channel SAN, a variety of servers connect to a variety of storage devices via the Fibre Channel fabric. Fibre Channel Arbitrated Loop (FCAL) architecture allows for up to 126 devices per loop, but throughput drops as devices are added because each node represents a latency factor against total loop performance. The attached storage devices form a pool and are externalized from the individual servers, allowing a large-scale storage subsystem to be shared among multiple host servers. Through a SAN, large numbers of users can simultaneously access data stored on a network of storage devices. Obviously, data sharing capabilities will become fundamental to the future of the SAN and management middle-ware will be key to its overall success. This architecture eliminates the bandwidth load caused by data transfers between servers and storage systems using slower network interfaces from the LAN.

The SAN storage devices can be disk arrays, tape devices and libraries, and tape or optical drives. In a SAN, the devices are not dedicated to any specific server enabling storage to be added as needed without disrupting server availability. The SAN architecture separates network traffic onto LANs and data traffic onto SANs.

SANs have gained notable industry momentum and excitement. They hold expectations to evolve toward global storage management capabilities and are expected to combine with NAS servers to become the ISAN--Intelligent Storage Area Network. We have just begun the SAN journey and many issues remain, including where the brains or management capability of the SAN, a SAN Operating System, will ultimately be located. The SAN model will lead the drive to fulfilling the long-awaited information utility promise.

COPYRIGHT 2000 West World Productions, Inc.
COPYRIGHT 2000 Gale Group