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The Starting Flag Drops for Serial Attached SCSI

The recent "plugfest" conducted by the SCSI Trade Association (STA) at the University of New Hampshire signaled the dropping of the commercial starting flag for Serial Attached SCSI (SAS) drives. Eighteen companies supplying everything from cables to expanders to host bus adapters (HBAs) to drives came together to physically test the SAS systems. "We think that was a good test point in terms of the maturity of the technology," says Harry Mason, president of STA and director of industry marketing for LSI Logic. "Now when we get together at the plug fests, there are actual racks and enclosures."

The four plugfests that STA has convened have served as convenient milestones to mark progress in this 3-year effort to develop a standard to update the 20-year-old parallel SCSI disk drive technology. The goal has been to provide universal interconnect with Serial ATA (SATA) drives while offering logical SCSI compatibility, reliability, performance, and manageability and to establish a foundation for another 20 years for performance enhancements. The third objective has been to address new storage needs, such as smaller form factors and dual-ported devices for greater availability.

Cables dominated the first plugfest. Small racks started to appear at the second event, and by the third plugfest, a limited number of larger racks were on hand. This most recent plugfest, Mason observes, hosted a good cross-section of racks from a fairly wide range of suppliers, including a 110-drive system that incorporated multiple hosts, expanders, and adapters talking to multiple disk drives. And although minor issues still emerged, by and large the systems worked as expected.

The next step for many storage vendors is to bring SAS to market. According to Mason, OEMs will offer SAS technology this summer as an option in their servers. And although he anticipates a significant number of SAS options on the market over the next several months, some OEMs are tying their SAS releases to the release of the next-generation Intel chipset, which is expected in the first half of 2006. SAS offerings should be available from the indirect channel (i.e., systems integrators and resellers) within the same timeframe.

If SAS technology continues to move forward as anticipated and works as expected, its prospects seem bright. According to John Monroe, a research vice president at Gartner, despite the strength of Fibre Channel and SATA technology, SAS should be the most prevalent multivolume hard-disk-drive interface by 2007. By 2009, he predicts, it should account for about 40 percent of the market.

There are several ways to look at the emergence of SAS. At one level, it represents the rejuvenation of enterprise-level direct-attached storage technology. SAS will clearly work its way into the places in which traditional SCSI drives have been used. Although the growth of NAS has been the storage community's focus for several years now, direct-attached storage is still the best alternative in many situations. The problem has been that traditional parallel SCSI technology was clearly becoming obsolete and difficult to manage while, at the same time, questions about the robustness of SATA have persisted.

SAS will also provide new options both to storage vendors and end users. "Vendors know that some percentage of their products need to support SATA drives and some percentage of their products need to support enterprise-class drives," Mason says. "Having the SAS infrastructure allows them to provision their products according to their customers' needs without having to develop an entirely new product." Mason predicts that SAS will serve as the infrastructure even in SATA-oriented systems.

For end users, SAS will enable a tiered storage model at a lower cost point than currently available. A single interface will support SATA for data tubs (i.e., large pools of low-cost storage) for staging to disks or tape as well as SAS for very high performance for transactional data environments. "You now have a single infrastructure that's capable of working in the tiered storage model. It's very cost-effective," said Linus Wong, strategic marketing director at Adaptec and an STA executive officer.

Despite SAS's progress, the development and educational process for the technology isn't quite over. Although SAS allows for interoperability with SATA, for example, it doesn't guarantee it. Both systems integrators and end users will have to do due diligence in putting systems together. Nevertheless, at the bottom line, SAS technology is ready to rock and roll. The components are ready. "The infrastructure is mature. It's just a matter of integrating it to systems to get to end users," said Wong

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