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iSCSI SANs: Page 3 of 6

In our test of TOE cards and iSCSI HBAs, (see "Don't Sink Your IP SAN" at www.nwc.com/1409/ 1409f3), we found that if a TOE card or HBA has only one target, it's unlikely to achieve a data rate of 100 Mbps because parallelism in the off-load processors prevent it.

Other factors in the TOE-versus-iSCSI-card debate include whether you intend to repurpose the card and whether the CPU on the server could benefit from the off-loading of other non-iSCSI TCP/IP processes.

Making a Choice

If these iSCSI drawbacks make you think twice, remember that Fibre Channel still remains the dominant SAN technology, and FC vendors have made great strides in their battle against almost legendary compatibility problems (see "High on Fibre" at www.nwc.com/1325/1325f5.html). In addition, much progress has been made in managing Fibre Channel hardware, though there is still much to do. For example, software tools that manage hardware from multiple vendors can only handle about 50 percent of the hardware out there. Interfaces and terminology from vendor to vendor still vary widely, especially regarding the names of specific kinds of ports. Bottom line: The Fibre Channel industry can't yet manage the number the ports on the outside of the chassis in the same manner.

If you've decided to bring iSCSI to your SAN, what's the best way to proceed? Start with the storage itself. All the usual considerations for a storage array come into play: reliability, speed, capacity, expandability and price.