Better grade for smart switches

There are only a few examples of application intelligence, but most intelligent-switch vendors are really promoting greater transport intelligence. For example, McData 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 serves Tier 1, an EMC Clariion CX700 from EMC Corp. is at Tier 2, and an EMC Centera is used for disk-based archiving.

Christian has redesigned the SAN with two i10Ks as the backbone. The other storage assets run through the McData director. Like many corporate users, though, the railroad remains cautious about adopting untried intelligence features.

"I'm buying the McData i10K to get I/O from here to here quickly, not for replication, backup or anything else," says Christian. "But it does take a lot of intelligence to move I/O efficiently in a SAN."

Packing the Trunk

In addition to boosting line speed, the latest brand of transportation intelligence includes trunking and path-selection features. For example, Brocade Communication Systems has made its Inter-Switch Link (ISL) Trunking software available as an optional add-on to its 4Gbit/sec. SilkWorm directors. ISLs that connect one switch to another can be combined to multiply the throughput -- i.e., four 2Gbit/sec. links become an 8Gbit/sec. line.

The San Diego Supercomputer Center (SDSC) at the University of California, San Diego, has deployed a Brocade SilkWorm 48000 director and plans to use this to implement trunking.

"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.

"VSANs allow different fabrics to exist on the same switch, and each is unaware of the existence of other fabrics," says Moore.

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