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6 Gbps SAS drives signal end of line for Fibre Channel disk drives

Carol Sliwa

The bell is tolling for Fibre Channel disk drives as 6 Gbps SAS drives begin their ascent in enterprise

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data storage systems. The big question left about Fibre Channel drives is when they will disappear entirely.

Fibre Channel has reached its final iteration as a hard disk drive (HDD) interface. While the roadmap for Fibre Channel connectivity from servers to storage via switches and host bus adapters calls for an increase from the current 8 Gbps to 16 Gbps next year and 32 Gbps soon after, disk manufacturers plan no upgrades beyond the current 4 Gbps Fibre Channel. By contrast, SAS roadmaps already lay out plans to go from 6 Gbps to 12 Gbps.

"Fibre Channel is dead. It's just a matter of time," said John Monroe, a research vice president in the storage group at Gartner Inc., in reference to the native HDD interface, not the Fibre Channel storage networking technology, which he said will likely live on for quite some time.

Gartner's market statistics for HDD interfaces show that unit shipments of 3 Gbps SAS overtook all rivals in 2007 -- at 40% -- followed by parallel and Serial ATA (SATA) at 27.8%, 4 Gbps Fibre Channel at 21.3% and parallel SCSI at 11%.

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Even though unit shipments of 4 Gbps Fibre Channel peaked at 9.4 million during 2008, market share dipped to 20.4% while 3 Gbps SAS increased to 43.5% and SATA climbed to 30.9%, according to Gartner.

The 2009 HDD statistics reflect the sea change that Gartner expects to play out over the next five years. SATA moved past SAS into first place at 43%, while SAS had 40% of the market with 3 Gbps making up 28.4% and the newly available 6 Gbps SAS at 11.6%. Fibre Channel continued its decline, with 15% of the overall market.

Gartner's market research projects that 4 Gbps Fibre Channel will fall to 10.1% this year and to 5.6% in 2011 en route to extinction in 2014. At that time, unit shipments of SATA (50.1%) and SAS (49.9%) will run neck-and-neck, and the SAS throughput speed will increase to 12 Gbps, according to Gartner.

IDC predicts vendors will discontinue shipments of Fibre Channel HDDs by 2013, a year earlier than Gartner's forecast. John Rydning, research director for HDDs at IDC, attributed the shift from Fibre Channel to SAS to vendors' desire to get to a common architecture. He said economies of scale will help to push down the overall cost of SAS components.

Rydning said the main sacrifice with the move from Fibre Channel to SAS is shorter cable lengths, but "most system OEMs have learned how to architect around the length limitations associated with SAS."

IDC's first-quarter statistics for "performance-optimized" enterprise-class HDDs — which excludes the slower SATA interface — showed 3 Gbps and 6 Gbps SAS comprised 72% of the market, followed by Fibre Channel at 27% and parallel SCSI at 1%.

SAS caught up to Fibre Channel as the dominant HDD interface for external enterprise data storage this year, IDC said. In the first quarter of 2010, the split was roughly 50-50 between Fibre Channel and SAS with 3.5-inch drives, while SAS dominated the market with the 2.5-inch form factor, according to Rydning.

"We expect that over the next two or three years, that 3.5-inch enterprise demand is going to continue to move to SAS and away from Fibre Channel," Rydning said. "By the time you get to 2013, we think the transition will be complete from Fibre Channel to SAS both for storage internal and storage external to servers."

Users begin the move to SAS for performance, cost-effectiveness reasons

Eddy Navarro, a computer systems manager at J. Craig Venter Institute (JCVI), a non-profit genomics research organization based in Rockville, Md., has already begun a move to SAS as a performance drive. JCVI's latest storage purchase, a NetApp FAS6080, has 15,000 3 Gbps SAS drives. JCVI also has 3 Gbps and 6 Gbps SAS disks for direct-attached storage (DAS) with a cluster of x86 servers with Nehalem processors.

"That's the direction things are going because it's much more cost efficient, and you're still really getting good performance," Navarro said. "Between the combination of solid-state disk and SAS, there's not much need for Fibre Channel drives anymore."

Teresa Worth, a senior product marketing manager in enterprise storage at hard drive manufacturer Seagate Technology LLC, said it's a "no brainer to go with the faster-speed" -- 6 Gbps SAS over 4 Gbps Fibre Channel. But Seagate still makes 3.5-inch 15,000 Fibre Channel drives and 2.5-inch 10,000 Fibre Channel drives to ease the migration path and provide flexibility for customers as they transition from 3.5-inch to 2.5-inch disks while shifting from Fibre Channel to SAS.

Worth said Seagate doesn't have an end-of-life date set for Fibre Channel drives and will continue to manufacture them as long as customers ask for them.

"There are still a lot of legacy systems out there that use Fibre Channel, and just because SAS is the new trend and where things are going and what the new systems are, that doesn't mean that those old systems are going to be defunct," Worth said.

Likewise, storage system vendors may be reluctant to set in stone dates for the discontinuance of Fibre Channel drive shipments. NetApp Inc., for instance, has made no final decision, according to Sandra Wu, a director of product marketing at the storage system vendor.

"We'll continue to observe our customers' purchase patterns," Wu said, noting that NetApp plans to add support for 6 Gbps SAS drives in a new disk drive family during the current calendar year. "We see Fibre Channel, with time, becoming a very small fraction of the storage technology order from us. It could be five years; it could be 10 years."

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