Is faster Fiber for you?
Rick Cook

Two gigabit-per-second fibre channel is finally here. Whether you should switch, and how soon, depends on your need for speed and forward compatibility versus your need to hold down costs and maintain compatibility.

At this fall's COMDEX, several companies, including

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Interphase Corp., Seagate Technology Inc., and Eurologic Systems demonstrated Fibre Channel products that operate at 2 gigabits-per-second (2Gbps) under the standard backed by the Fibre Channel Industry Association (FCIA). Most of the other major vendors of Fibre Channel storage equipment, such as IBM subsidiary Mylex Corp. have announced 2-Gbps products to ship either in this quarter or next year.

The 2Gbps standard is a straightforward extension of the current Fibre Channel with a speed of 2.12 GHz and a full-duplex bandwidth of 400 megabytes-per-second (MBps). The 2 Gbps is designed to be backward compatible and offer all the topologies and protocols available at 1 Gbps. The vendors are stressing fiber optic cabling for the new standard rather than copper because of cross-talk considerations.

In spite of the similarity in the two flavors of Fibre Channel there are several drawbacks to 2-Gbps Fibre Channel. One of the most significant, besides added cost of components, is that you can't mix 2-Gbps and 1-Gbps Fibre Channel devices on the same link without slowing the entire circuit down to 1 Gbps. However you can use 1- and 2-Gbps devices in the same network if you isolate the links. For example, you can use a switch with separate ports for 1-Gbps and 2-Gbps devices, or you can put the high-speed and low-speed devices on separate loops. Of course this complicates the networks but it saves buying an entirely new SAN.

Fibre Channel vendors point out that customers can plan for the future by purchasing 2-Gbps components or 2-Gbps-ready components now to ease their future upgrade path. However storage managers have to balance the added costs today against the cost of later upgrades, if and when. This is especially true since 2-Gbps products are only beginning to appear in quantity and significant adoption probably won't take place until the middle of 2001.

About the author: Rick Cook has been writing about mass storage since the days when the term meant an 80K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last twenty years he has been a freelance writer specializing in storage and other computer issues.

This was first published in January 2001

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