"With a 4Gbit/sec. switch, you can trunk together eight ports to get up to 32Gbit/sec.," says Bryan Banister, manager of storage systems and production servers at SDSC. "But we'll need to add extra 48000s to achieve this."

In the meantime, he has found a performance benefit of about 1Gbit/sec. using another intelligent transportation enhancement built into the director. The technology, known as Dynamic Path Selection, automatically routes data to the most efficient path available. This feature can also reduce the number of ISLs needed.

Other switch vendors are releasing similar products. McData switches, for instance, contain trunking technology, and Norfolk Southern has taken advantage of that feature to tie four of its 2Gbit/sec. McData 3232 switches into an 8Gbit/sec. trunk.

Still another largely transportation-based intelligence feature is known by a variety of terms, including virtual SAN (VSAN), dynamic partitioning or SAN routing. The idea is to split one SAN up into multiple discrete sections or tie several SANs into one central switch. This solves problems such as having low utilization on one tape system and overutilization on another.

With a VSAN, one switch -- such as a McData i10K -- can be partitioned into logical segments, and utilization rates can be optimized. Similarly, one part of the SAN can be earmarked to run at 4Gbit/sec. for backup while the rest runs at 2Gbit/sec. Management is also simplified, and access rights can be set for each partition.