Although switches are normally associated with more costly Fibre Channel fabric configurations, several manufacturers now offer switches for use in Fibre Channel-Arbitrated Loop (FC-AL) SANs. These are true switches that use the more familiar FC-AL protocol but offer more capability than the hubs or concentrators sometimes used in FC-AL networks.
An FC-AL switch is an intermediate solution, offering more flexibility than a simple FC-AL loop or an FC-AL with a hub or concentrator, but not as fast or as flexible as a Fabric Switch. Upgrading from a SAN with an FC-AL switch to a Fabric SAN is still a complicated procedure that will often involve either replacing or significantly upgrading the FC-AL switches. That said, makers of FC-AL switches claim they can offer some of the benefits of a Fibre Channel Fabric at a much lower cost. The advantages include the ability to zone a SAN into two or more subnetworks, and the ability to make more than one connection concurrently.
Among the companies offering FC-AL SAN switches, Gadzoox is promoting its products the most aggressively. Switches are also available from Brocade in its Silkworm series and from Compaq.
- Gadzoox has a few white papers outlining the advantages of FC-AL switches when used with SANs. These can be found at: http://www.mti.com/documents/reports/whitepapers/wp98004.pdf and at . http://www.gadzoox.com/pdf/SSWP'JW0399.pdf (Before you can view these, you'll need to install Adobe Acrobat Reader.)
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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 free-lance writer specializing in storage and other computer issues.