The current wave of intelligence, however, generally refers to higher-end switches known as directors. Today's director-class switches contain two types of intelligence: transport intelligence and application intelligence.

Transport intelligence provides enhancements for moving data through the storage fabric while optimizing throughput. The functions mentioned above can be classified as transport intelligence. Such features have been strengthened in the newest directors, which also include a new brand of transportation smarts, such as the ability to handle virtualization and the partitioning of resources.

Application intelligence, on the other hand, provides higher-level storage services, such as storage virtualization, continuous data protection, and backup and recovery.

There are only a few examples of application intelligence, but most intelligent-switch vendors are really promoting greater transport intelligence. For example, Broomfield, Colo.-based McData Corp. offers the Intrepid 10000 Director (i10K). Compared with the previous-generation directors, the i10K comes with advanced transport intelligence intended to speed up traffic.

Norfolk Southern is introducing an i10K into its environment. The current storage-area network (SAN) serves two data centers that represent 500-plus Unix servers (mainly AIX) and more than 600 Windows-based servers. The core of the SAN is built around four McData 6140 directors (two at each site) as well as a series of smaller McData 3232 switches at the edge of the SAN. It is also served by multiple tiers of data. An HDS 9980 array from Hitachi Data Systems Corp. serves Tier 1, an EMC Clariion CX700 from EMC Corp. is at Tier 2, and an EMC Centera is used for disk-based archiving.