Gadzoox Weaves Fabric into SAN Switches

Because they use different protocols than standard LANs or WANs, to this point SANs have been limited in their reach. In addition, SAN hardware is extremely specialized, and rarely can be repurposed for different applications. Combined with the lack of standardization in SANs, these factors can scare away many administrators that might otherwise be interested in deploying a SAN.

In reaction to these issues, Gadzoox Networks Inc. ( added fabric switching to its Capellix switch, which previously supported only loop switching. In addition, the company introduced the Xport plug-in module that allows connection between SAN nodes up to 8 kilometers.

Loop and fabric switching are two different flavors of SAN switching for distinct purposes: Loop switching is used for switching within a small SAN or a small area within a SAN; Fabric switching is used for the backbones of large SANs.

Loop switches are limited in their functionality. They support only 128 nodes, offer no name services, and have limited throughput flexibility. They adequately do what they are designed for, but their scalability is questionable.

By contrast, fabric switches are designed for backbone applications, they offer unlimited nodes, name services, and further bandwidth options. While some fabric switches can act as loop switches with emulation, the SAN suffers performance problems -- it is like using a backhoe for a hand trowel.

Gadzoox took a different approach when it created a dual loop/fabric switch: The company added fabric functionality to its current loop switch Capellix.

Robert Gray, research director for storage systems at IDC (, believes that the addition of Fabric switching to Capellix will enable users to create more scalable SANs. "It’s about being able to scale and not having to forklift your equipment."

Gadzoox points out that now that SANs are being adopted in enterprise systems, administrators will become more interested in connecting the disparate SANs, or data islands, as Gadzoox deems them.

This is accomplished through fabric switches, which enable SANs to interconnect over WANs. Gadzoox’s play will allow users to purchase loop equipment, then later scale up to fabric-based SANs.

SANs use Fibre Channel protocols for transmitting data, and are limited by the distances over which they can function. Unlike Ethernet of IP protocols, where the emphasis is placed on error correction, Fibre Channel requires that blocks of data arrive in the right order and focuses on moving large amounts of data quickly. When data islands are separated by large geographical distances, the signal stands a greater chance of degradation.

In addition, Fibre Channel relies on filling the bandwidth with as much data as possible, creating a uninterrupted stream of data. A cable several miles long will hold more data in transit than most SAN hardware is designed to handle, so latency issues can affect SAN performance.

Fibre Channel and SAN technologies don’t like latency," confirms Steve Duplessie, an analyst at Enterprise Storage Group ( He says other vendors offer the ability to transmit Fibre Channel 80 kilometers, but "not without repeaters, today." He adds that repeaters create issues with ports that Gadzoox's Xport module overcomes.

Gadzoox’s Xport module can further extend the functionality of a Capellix switch used for fabric switching. The module offers a large buffer for reducing the latency is physically distant transfers. Because the module stores extra data in the buffer, there are no spurts in the transmission due to the extra distance.

While SANs are just beginning to gain momentum, Gray expects the market for SANs to explode. In 1999 the market was $1.4 million. Gray believes that by 2003, the market will expand to $10 billion.

Gadzoox, whose market was confined to the internal workings of SANs, is making a bold play for the larger market by introducing fabric switching and long transmissions.

"Brocade has won the OEM war," Duplessie declares, suggesting that Gadzoox will need to find other markets for its gear. Duplessie believes Gadzoox is primed to compete for upgrades and point solutions for users who already have their SANs in place.

Capellix, with fabric switching services, and the Xport module, offer administrators the ability to extend the value of their SANs.