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Insider Compares SAS & Fibre Channel

Serial Attached SCSI (SAS) stands to replace the parallel Small Computer System Interface (SCSI) technology that has reached the end of its shelf life. The next question is: Will it replace Fibre Channel?

According to the latest Byte and Switch Insider report, SAS and Fibre Channel are neck and neck in terms of features, with one or the other providing an advantage in key areas. When it comes to speed, for instance, SAS offers a data transfer rate of 3 Gbit/s, while Fibre Channel offers 4 Gbit/s. Both offer similar performance and connectivity features as well.

"For the moment, it is hard to differentiate between the technologies on performance or reliability, though cost presents a different argument," states report author Martin Courtney.

SAS can be 25 percent to 50 percent cheaper than Fibre Channel, because it has cheaper components, the report states. What's more, 3.5-inch Fibre Channel disks cost more compared with 2.5-inch SAS units, and drive manufacturers claim smaller units use less power. SAS is also compatible with SATA for tiered storage environments, while Fibre Channel is not.

But it's still tough to make a storage area network based on SAS, the report points out. Adaptec, LSI, PMC-Sierra, and Vitesse make expanders that connect multiple SAS devices to a limited number of host ports. Some of these expanders can be used in fan-out configurations to support tens of thousands of devices, albeit at a distance range of 8 meters.

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