Souping Up SATA

Coming drives will be not exactly Fibre Channel, but an improvement on today's SATA gear

March 17, 2005

4 Min Read
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SATA drives, originally developed as disk for low-cost desktops, are picking up features to make them more enterprise-friendly.

Industry standards group SATA-International Organization (SATA-IO) recently completed its fourth plugfest, drawing 61 vendors to Portland, Ore. Knut Grimsrud, Intel Corp. (Nasdaq: INTC) principal engineer and SATA-IO president, pronounced the major new technologies such as 3-Gbit/s bandwidth and Native Command Queuing (NCQ) ready to go.

What will these new features mean for SATA? Driven by a rise in disk backup and ILM, SATA drives have caught on in the enterprise largely as secondary storage. But even the new features wont help SATA replace Fibre Channel and SCSI as primary enterprise drives. They might persuade enterprise administrators to take SATA more seriously as part of a tiered storage approach, especially considering the new features aren’t expected to add to SATA’s price tag.

“This will make it easier for IT to see SATA as something that belongs on the enterprise floor,” says analyst Mike Karp of Enterprise Management Associates. “If a SATA device is maybe not as robust as SAS or Fibre Channel, IT managers are still going to have to look at it and say, ‘I can do the math. It’s 40 percent cheaper, and that’s a pretty compelling argument even if I have to keep replacing drives.’ ”

Before we get into the new features, let’s clear up a misconception. There’s no such technology as SATA II, although vendors commonly use the term as an umbrella for SATA’s advanced features. SATA II was the name of the standards group that has turned into SATA-IO. So just because a product is billed as SATA II, it doesn’t mean it supports all of its new features.“SATA II is a misnomer,” Grimsrud says. “We try not to use the term SATA II. We use the names for the features. Some people refer to 3-gig as SATA II. We refer to it as 3-gig signaling.”

SATA’s most useful new performance features are 3-gig bandwidth and NCQ. At 3-gig, SATA drives will have twice as much bandwidth as the original drives and they will be backwards compatible with 1.5-gig drives. Drive manufacturers such as Hitachi Global Storage Technologies (Hitachi GST), Maxtor Corp. (NYSE: MXO), and Seagate Technology Inc. (NYSE: STX) expect 3-gig SATA drives around mid year. That would put SATA on par with the first version of serial attached SCSI (SAS) drives that will ship later this year at 3-gig.

Fibre Channel drives will go from 2- to 4-Gbit/s this year, probably soon after 3-Gbit/s SATA. After that, Fibre Channel’s next stop with be at least 8-Gbit/s and maybe 10-Gbit/s, while Grimsrud says SATA’s next step will be to double bandwidth to 6-Gbit/s.

NCQ minimizes the number of I/O interrupts a server makes on the drive when carrying out multiple commands. It lets the server complete 32 commands without interruption. First-generation SATA required the host to interrupt the process before every command. NCQ also reduces wear and tear on the drives. Fibre Channel and SCSI already support NCQ, and Seagate SATA drives have supported it since last year. NCQ is just beginning to show up in other SATA devices, and NCQ interoperability was a major focus of the recent plugfest. “NCQ is looking sound,” Grimsrud says. “I foresee no future hiccups.”

New SATA drives will also support hot plug and staggered spin-up capabilities to boost reliability. Hot plug allows a user to swap out a failed drive or add a new drive without taking down all the drives in an array. Staggered spin-up lets users control the sequence that drives power up, avoiding the massive power drain caused by all drives starting simultaneously. These features are available in Fibre Channel and SCSI drives, and even some of the newer SATA drives.Along with its new features, SATA can get a boost in the enterprise from its coexistence with SAS in the same backplane. That will facilitate tiered storage.

“Are these new [SATA] drives suitable for primary storage?” asks Doug Pickford, Hitachi GST director of product strategy. “Certainly some people will take a shot at that. But it’s really the marriage of SAS and SATA that satisfies the greatest breadth of enterprise needs.”

An even newer technology that could make it cheaper to implement tiered storage is SATA Tunneling Over Fibre Channel that Emulex Corp. (NYSE: ELX) announced this week (see Emulex Tunnels SATA Over FC). The technology would replace a translator card needed to bridge Fibre Channel and SATA drives. Emulex has yet to present it to the American National Standards Institute (ANSI) T11 board for inclusion into the Fibre Channel protocol as an industry standard.

— Dave Raffo, Senior Editor, Byte and Switch

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