Fibre Channel Directors: Myths, Realities, and Evaluations Page 5


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Enterprise-class Fibre Channel directors should be compared with the core IP routers and switches at any site. Access to the Internet and the other machines in your network is useless unless you can access your data. From what I have seen, many managers do not look at things this way. They focus on the cost difference between the two switch types without thinking about the data access issues and without closely looking at the feature list comparison.

Part of the problem is the lack of a definition for these switches, which does not help the consumer nor, in my opinion, the vendors, as they have to sell against each other without even a baseline set of features and functions. Perhaps it's because the concept of a Fibre Channel director is far newer than the concept of an Internet core switch or router. In any event, this leads to problems for everyone involved.

When it comes to performance for director-class switches, you must clearly define your application performance. Two-gigabit full duplex performance from any port to any port is not always available in these switches, but aside from all but a few applications, is this even necessary?

Two areas important to consider are tape drives and backup or HSM applications. Most of the time from what I have seen, tapes are configured with one HBA trying to write/read the data at full data rate. Take, for example, the STK T9940B tape drive with a rated uncompressed speed at 30 MB/sec and a rated compressed speed of ~70 MB/sec. Even though the database system might not ever have 2 Gb performance issues for the database activity, performance could become an issue for the backups. Or if you have high data compression and have bound 3 tape drives to an HBA using different parts of the switch, performance could become a factor in this case as well.

Asking vendors hard questions about the features and functions that you want and need is your responsibility, as there really are no standards in place at this point. In other words, Caveat Emptor – Let the Buyer Beware.

» See All Articles by Columnist Henry Newman

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