Drives With SAS

A new category of disk drives will start appearing in volume in the channel this fall, promising to reshape the market of storage subsystems. Based on a new standard called Serial-Attached SCSI (SAS), these long-awaited drives will provide a new tier of storage in the midrange, while offering alternatives to more costly high-end systems.

Experts are predicting SAS drives will be the hottest storage media to come along since Serial ATA (SATA), its lower-end counterpart, while offering a lower-cost alternative to Fibre Channel drives, its higher-end counterpart. Hewlett-Packard and IBM have already begun offering SAS drives as an option in select servers, and they're likely to become standard by the end of 2006--much like SATA replaced ATA drives on all but the lowest end PCs.

Market researcher IDC predicts SAS drives will grow from virtually nothing last year, to 7 percent of disks shipped worldwide this year, and 17 percent in 2006; by 2008, SAS drives could account for more than one-third of all disk drives shipped (see "HDD Forecast," page 48).

"[SAS] will be the foundation of high-end enterprise storage going forward over the next several years," says Sam Sawyer, Hitachi's senior adviser for product planning and strategy. "It's the key ingredient to enabling some new approaches to tiered storage."

id
unit-1659132512259
type
Sponsored post

SAS Benefits

SAS will ultimately replace traditional Parallel SCSI drives, which have been around for the better part of two decades and have reached their limit at 320 Mbps. SAS drives, on the other hand, will have much more throughput and higher levels of performance. It will support connectivity approximately 10 times more than its predecessor--up to 3 Gbps--with a planned doubling during the next 18 months. Most notably, SAS drives feature dual ports, so they can send and receive data simultaneously, or serially. SAS drives support speeds of up to 15,000 RPM, double that of SATA drives.

From a cost perspective, SAS drives will be priced similarly to Parallel SCSI drives, and be far less expensive than Fibre Channel drives and related infrastructure.

"I don't see [SAS] phasing out Fibre Channel for awhile, but I do see it taking part of that market share and some of the market of SATA," says Mark Spear, vice president of sales at Cross Circuit, a Santa Clara, Calif.-based networking and storage VAR that plans on offering new SAS-based controllers and host-bus adapters from Adaptec. "That said, I think it's really going to have a big impact."

SAS drives have another key advantage: Its cabling is much thinner than the wide wires of its predecessor. In addition, storage VARs can build arrays consisting of both SAS and SATA drives for tiered solutions because the same cabling interoperates with a common backplane. In fact, most of the key drive and host-bus adapter vendors are touting that benefit.

"We think they are complementary solutions," says Harry Mason, director of industry marketing at LSI Logic and president of the SCSI Trade Association's board of directors. "They solve a need in the marketplace to take a common set of components and provision for whatever storage application environment you need."

For its part, LSI Logic has conducted numerous interoperability tests and demonstrations with Fujitsu and Maxtor, running both SAS and SATA drives on a common backplane.

"The SAS backplane and infrastructure allows for SATA protocols to travel over the same wires," says Don Jeanette, Fujitsu's senior product marketing manager.

Fujitsu and LSI Logic recently said they will bundle their respective components. The bundle includes LSI's expanders with up to eight of Fujitsu's new 2.5-inch MAV2073RC SAS-based drives.

"I think you'll see some incremental growth this quarter and next," says Joel Hagberg, Fujitsu's vice president of marketing and business development. Early next year, Hagberg expects SAS to gain critical mass when Intel releases its Blackford chip set in which support for SAS is embedded onto the motherboard. "At that point, every major refresh from the five top server companies will move completely to SAS," he says.

Will SAS Upstage Fibre Channel?

Not everyone, however, is bullish on SAS, particularly those vendors with a more vested interest in Fibre Channel, such as Emulex and Qlogic.

"SAS, for the most part, is really an unproven technology," says Bob Brencic, senior director of switch marketing at Emulex, which earlier this year proposed an alternative solution called SATA Tunneling over Fibre Channel (FC-SATA). FC-SATA would allow VARs to embed SATA drives into Fibre Channel-based systems. By providing multiple initiators to a SATA drive, Brencic says FC-SATA will have better failover capabilities than SAS. ANSI's T11 Committee has formed a working group to add FC-SATA to the Fibre Channel standard. Disk drives based on the technology, however, are not likely to reach the market until 2007.

Given that several key tier-one storage systems vendors have not indicated how, or if, SAS will fit into their high-end arrays, FC-SATA could be a viable alternative. EMC's recently launched Symmetrix DMX-3 system will support tiered storage based on SATA drives, the company says.

Nonetheless, SAS will take center stage in the drive world for the next few months. IBM already began offering its first SAS-based drive in its eServer x366 in February, followed by the x460 in June and x260 in August. For its part, HP recently rolled its first ProLiant servers with SAS drives, and high-speed 2.5-inch drives are planned for early next year. HP is also planning to offer SAS drives in its StorageWorks Modular Smart Array.

Other vendors on board include Maxtor, which is shipping its Atlas 3.5-inch SAS drives; Fujitsu, which has launched a 2.5-inch SAS drive and is expected to release a 3.5-inch SAS drive; Hitachi, which is shipping its SAS-based 15K147 drives; and Seagate, which is shipping its Savvio 10K.1 SAS drive, and the Cheetah 15K.4 Se.

Of course, it takes more than drives to make a solution. In addition to Adaptec and LSI Logic, which are rolling out controllers, expanders and host-bus adapters to systems builders and OEM partners, Ario Data Networks last month unveiled a RAID controller that supports SAS and SATA and connects to 4-Gbps Fibre-Channel hosts. And Broadcom is readying its BCM8603 RAID-on-Chip product that integrates both a SAS and SATA controller on a common chip set.

As SAS drives work their way into the channel, they will serve as a new option to tiered storage solutions. Their interoperability with SATA controllers, coupled with improved performance, will no doubt alter SCSI as it was once known, while putting new pressures on the high end.