Section 4.9. Fibre Channel Interoperability

   

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4.9 Fibre Channel Interoperability

The phrase "let the buyer beware" summarizes the state of interoperability in the Fibre Channel world.

That said, one can say that most of the problems in interoperability for FC-AL configurations have been ironed out by work done by storage device, HBA, FC-AL switch, and router vendors. A lot of testing is done by device vendors, original equipment manufacturers, and solution provider vendors , but the basic situation is that although in theory interoperability is supposed to work, in practice a fair amount of time is spent testing and tweaking configurations to make them work. It is advisable to stick to configurations that have been tested by a solution provider or vendor.

The biggest problem is that adherence to standards is not necessarily guaranteed . In addition, adherence to standards does not guarantee interoperability either.

Solution providers such as IBM, HP, and EMC set up labs to test interoperability among various devices and then certify the solution. To a degree, various device vendors do so as well. One is well advised to stick to these certified solutions, thereby avoiding the problems that frequently arise when a device that is not part of this certified solution is added.

Although the overwhelming majority of FC SANs installed are operating at a speed of 1 Gbps, the first of the 2-Gbps SAN devices are now making a commercial appearance, bringing with them some new interoperability problems. The standards followed by vendors attempt to operate at 2 Gbps, but these devices revert to 1 Gbps when the devices with which they are attempting to communicate are capable of only 1 Gbps. Actually, an FC SAN is expected to operate at the speed of the slowest device within the SAN. Thus, if there is even a single 1-Gbps device in the SAN, the SAN will operate at 1 Gbps.

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