Fibre Channel Directors: Myths, Realities, and Evaluations


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A great deal has been written about Fibre Channel directors in a number of reputable publications, but how exactly is a FC director-class switch different than a standard switch? The answer is not as clear as you might think. The place I usually go for Fibre Channel definitions is:


The Storage Networking Industry Association (SNIA) is known as the place to go for definitions of common and esoteric terms for storage. These definitions are agreed upon by the SNIA membership, so in effect they are defacto terms the industry has defined and uses. Unfortunately, this was strike one, as SNIA at this time has no definition in place for a Fibre Channel director. So next I performed a GOOGLE search using:


The result was a number of hits — some useful, some useless; here is one site that had an actual definition:


I had actually never heard of this site, but here is how they define a director-class switch:

Director-class switch
A fault-tolerant Fibre Channel switch that typically has a high port count and may serve as a central switch to other fabrics.

Of course, since this definition is about as clear as the Mississippi River in New Orleans after a spring flood, I thought it might be useful to review some of the issues and considerations with director-class switches. First, though, it's important to note that:

  1. The SNIA members do not want to commit to a definition for director-class switches at this time
  2. The TechWeb definition and a few others that I have found (many of them vendor-based) leave a huge amount of wiggle room for the vendors and are often contradictory

Page 2: So What Exactly Is a Director?

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