Friday, December 12, 2008

Arbitrated Loop

FC-AL was actually an add-on to the original FC specification which consists of Point-to-point and Fabric topologies. This is introduced as the cost for fabric is quite high and point-to-point limits the number of device connecting. FC-AL can be constructed by using NL Ports (host or storage devices) connected by fiber optic cables with SC connectors that can be split. It is an inexpensive way to connect several disk to a host. One disadvantage of this configuration is it is only practical with short distances due to logistical problem. Another problem is one bad HBA or cable can take out the entire network.

A better configuration is star layout. The connectors do not need to be split. A hub will make sure the transmit and receive ends are matched up. A manged hub can also prune the node in the event of a failure.

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