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General Information
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May 13, 2005
• Vol.27 Issue 19
Page(s) 1 in print issue
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Vendors Bring SAS To The Starting Gate
High-Speed & Flexible Storage After Years Of Development
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After much industry discussion and development, OEMs are finally bringing SAS storage to market. So what does this mean for IT admins’ storage needs?
SAS’ main benefits include increased data rate transfer speeds and flexibility compared to SATA, which is limited to single connections. Building on SCSI technologies, SAS also offers longer cable distances, increased stability, and backward compatibility with SCSI and SATA devices.
“The IT end-user benefits of using SAS-based servers or arrays over parallel SCSI are significant. SAS-based systems will deliver throughput performance, scalability for increased capacity, and flexibility with the use of SATA or SAS drives in an SAS system that are not possible with traditional parallel SCSI systems,” says Bill Schilling, director of Global Product Marketing for Enterprise Storage at Seagate Technology.
 An SAS & SATA Marriage?
But while SAS is often seen as the new-generation replacement technology for SATA, it will not likely render SATA obsolete, at least in the near term, observers say.
“SAS is aimed at a different marketplace than SATA,” says John A. Fobel, vice president for Rancho, a manufacturer of computer peripheral products. “SATA is [geared for] desktop PC and low-end server markets. SATA hard disks, for example, are for lower performance [applications] and are less costly.”
 Indeed, some developers say that SAS and SATA will not only coexist but will serve to complement each other. “SAS and SATA will work together harmoniously, unlike any other storage technologies have done before. For example, when using an SAS-based system, SATA drives can be added into that same system or box without any need to change the infrastructure or cabling. . . . Conversely, a SATA-based system will not be able to accept SAS drives, since it only works when an SAS system is used as a base,” Schilling says. “This ultimately means that IT managers can customize their storage to the types of applications that they run and use a tiered-storage model. Essentially, SAS drives can be used for business-critical data that must be run 24/7 or deliver the fastest transaction I/O responses, while SATA drives can be used in the same system for backup or secondary bulk storage purposes.”
What SAS Offers Now
This is the first year IT admins can select from a wide range of commercially available offerings of SAS equipment and devices, while the technology still represents something new. At the Intel Developer’s Forum in March, the STA (SCSI Trade Association) displayed what it called the first-ever SAS performance demonstration of a single-RAID array across multiple SAS controllers. The RAID-on-chip SAS controller offered eight ports and both PCI-X and PCI-Express interfaces. The 12rpm disk drives maintained a 1GBps data transfer rate, which STA claimed was the fastest public demonstration of an SAS system to date. Each drive could sustain up to 93.3MBps, providing a combined total of 1GBps throughput, STA said.
Rancho introduced 12X SAS fanout and edge expanders in January and plans to launch its SAS JBOD enclosures for 2.5-inch hard disks in May. It will release its SAS 24X and 36X fanout expanders by midyear.
Rancho’s 12-port, 3 Gb RTSA-SRFO-2X fanout and edge expander can accommodate connecting targets and initiators with up to 12 integrated phys and can support narrow and wide port configurations. The RTSASRFO-12X can also be used in simple topologies to attach an initiator to SAS/SATA devices, in edge expander topologies to increase the number of accessible devices or in fault tolerant path redundancy topologies to improve system reliability, Rancho says.
“I think you will start seeing SAS hard disks on the market around June,” Rancho’s Fobel says. “SAS tape drives may be available as early as December. They always lag the hard disks.”
Seagate began shipping SAS drives to large OEMs for qualification in November, Schilling says. “The rest of the SAS infrastructure required for system release should be final and begin to emerge by the end of this current calendar quarter,” Schilling notes. “At that time Seagate plans to release SAS drives into the channel for general availability, since this will be timed appropriately with the rest of the industry building its own SAS solutions.”
Earlier this year Adaptec said that IBM’s recently launched X3 architecture and eServer xSeries 366 solution incorporates its SAS RAID controller for Intel Xeon processor-based servers. Adaptec also said IBM was the first major vendor to ship a high-performance server based on its SAS technology and RAID 6 data protection. Adaptec plans to expand its SAS product offerings, which will include host to networked storage solutions.
Maxtor said earlier this year that test units of its SAS interface are available with its Atlas 10K V and Atlas 15K II drives. It has already shipped qualification units to several undisclosed OEMs as well as to more than 30 system manufacturers. Qualification units shipped include what the company maintains are the industry’s first 300GB SAS drives, the Atlas 10K V. 
by Bruce Gain
SAS’ Feature Checklist
As SAS storage devices become more readily available this year, they will offer a number of new features to address high-end applications for which speed and versatility are crucial. Their capabilities and features include:
• Compatibility between SAS and SATA, allowing for tiered storage in a single and shared enclosure
• Dual-port connectivity with up to 128 drives and data transfer rates of 3Gbps for both connections
• Low-cost switches, known as expanders, which can aggregate hundreds of drives
SOURCE: SEAGATE |
SAS’ Niche
SAS was developed to meet the needs of future I/O and direct-attach storage applications, according to the SCSI Trade Association. But instead of replacing SATA, SAS is intended to complement and serve as a universal interconnect with SATA. Indeed, SATA will likely meet the storage needs of more cost-sensitive applications, while high-powered SAS devices will offer data rate transfer speeds, robustness, and versatility required by more mission-critical and high-end storage applications. |
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