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Solid-state drives aim to edge out HDDs

Posted: 16 Jan 2008 ?? ?Print Version ?Bookmark and Share

Keywords:solid state drive? SSD? HDD? NAND flash?

The landscape is shifting in the emerging market for solid-state storage drives (SSDs). Micron Technology Inc. last November entered the fray, and Toshiba Corp. stands poised to join the rapidly crowding field, whose proponents promise to propel the technology into the mainstream PC market at the expense of the lowly hard drive.

Based on standard NAND flash, SSDs constitute a new class of rugged, low-power systems that could threaten power-hungry HDDs, whose mechanical parts make them susceptible to failures in the field. But analysts differ on when flash-based storage might make headway in mainstream PCs, since OEMs face cost and design barriers, including the lack of NAND controllers optimized for drive applications and the write-cycle limitations of multilevel-cell (MLC) NAND flash.

In some cases, today's SSDs provide less performance and are up to 45 times more expensive than rival hard drives in PC, industrial and related storage applications. Meanwhile, thanks to perpendicular recording technology and other futuristic schemes, workhorse hard drives are expected to continue to scale for several years, possibly pushing out the need for SSDs to the next decade.

SSDs must make dramatic improvements in both cost and design before the PC community will consider widespread adoption, said analyst Joseph Unsworth at Gartner Inc. He foresees a long "education process" before OEMs and end users understand the benefits of SSDs for notebooks, desktops and server farms. Unsworth puts the tipping point for SSDs at 2009, though other analysts do not expect widespread adoption until 2011 or 2012.

Most SSDs today are niche-oriented products sold into "non-traditional" drive markets such as the industrial and military sectors, said Jeffrey Janukowicz, an analyst at International Data Corp. PC OEMs like Dell Inc. and Hewlett-Packard Co. offer SSDs as an option for their systems, but the solutions are often expensive and are not widely advertised on vendors' Websites. A 32Gbyte SSD sells for some $350, while a 160Gbyte hard drive goes for less than $100, Janukowicz noted.

Magic price point
Alan Niebel, CEO of Web-Feet Research Inc., put the average cost per gigabyte at $10 for SSDs and 30 cents for hard drives. "If you want to see big adoption of SSDs, they must hit $1 per gigabyte," Niebel said. He doesn't expect that magic price point to arrive before 2011?and by that time, hard drives are expected to cost a mere 10 cents, and perhaps as little as 3 cents or 4 cents, per gigabyte of storage.

At present, the SSD market is dominated by smaller players, such as BiTMicro Networks Inc., Mtron C. Ltd, Super Talent Technology Corp. and Stec Inc. These vendors do not have fabs and must procure NAND parts from outside suppliers. And only a few of the SSD vendors develop their own controller technologies.

But the potential for PC market adoption of solid-state drives is changing the SSD landscape. Some 40 vendors are already chasing a total SSD market that IDC expects to grow from $373 million in 2006 to $5.4 billion by 2011. Intel Corp., SanDisk Corp. and Samsung Electronics Co. Ltd have also rolled out SSD products. Now, Micron has tossed its hat in the ring, and Toshiba may be next.

For Intel, Micron and Toshiba, SSDs represent a new NAND growth driver and an avenue to sell their internal capacity. Even the disk drive community is seeing the SSD light, with Seagate and others expected to enter the fray this year. Most of the chip and drive giants are developing their own controllers.

The eventual winners in the marketplace? It's too early to tell, but some see a shakeout on the horizon.

"Obviously, the fabs guys have a cost advantage," said Niebel. "But you will still need to have the critical intellectual property and controller technology" to succeed.

Looming price war?
As the larger players take the field, averaging selling prices for SSDs are expected to fall. Some even foresee a price war, especially with Samsung's thrust and the eventual entry of Toshiba. The two companies are fierce rivals in NAND and regularly battle on price.

Smaller SSD vendors say they welcome the new entries. "By the end of 2008, we will have a better view of the whole landscape," said Patrick Wilkison, VP of marketing and business development at Stec, an integrator that claimed it had 40 percent of the $260 million market for flash drives in 2005. "The more large, viable vendors there are, the more it bolsters this new category."

Wilkison believes flash chip makers could command low-end sales to PCs because of their component-cost advantage. Server drives are more of a systems-level product, requiring expertise that favors the integrators and hard drive makers, he said.

The flash makers generally have a more narrow product family at lower performance ratings, Wilkison said. Stec's portfolio spans drives from 8Gbytes to 512Gbytes in capacity and offers higher transfer rates than most competitors, he said. The lineup includes models supporting parallel and serial ATA as well as Fibre Channel interfaces. Drives supporting the serial-attached SCSI interface are now in the works.

Penetration of SSDs in notebook PCs seen taking off.

Hard drive vendors like Seagate also face challenges. "The hard drive makers are not sure where this SSD momentum is going to stop and are concerned about losing a piece of the 2.5-inch drive business," said Wilkison. Already, four drive makers have canceled plans for 1-inch and smaller hard drives because of the competition from flash. Analysts said 1.8-inch drives are also under assault.

Still, there is some debate whether the pieces are in place to bring down the cost of SSDs to an affordable level.

Doug Freedman, an analyst with American Technology Research Inc., projected in a report that SSDs "will eventually dominate the mobile market. While currently cost-prohibitive in the mainstream mobile market, SSDs are more competitive on price than enterprise-class HDDs when compared on a total-cost-of-ownership basis and as an add-on to improve current network storage performance and reliability."

In 2008, SSDs are projected to penetrate about 5 percent of the overall notebook market. That equates to some 5 million units, or about 200 million gigabytes of storage density, according to the report.

Design hurdles
Such activity notwithstanding, major hurdles still stand in the way of mass adoption of SSDs. Aside from cost, the sticking points include controller technology, software integration and NAND technology itself.

One question is whether NAND prices can fall fast enough to keep up with magnetic media on a density basis. For years, NAND prices have dropped by an average of 40 percent or more per year. "With cost being the biggest barrier to penetration in consumer products, we believe a 50 percent year-over-year ASP decline in NAND is critical to mass adoption in 2009 to 2010," Freedman said.

But another hurdle "in addition to price?and probably more important in the short run, regardless of price?is the lack of drivers and controller technology needed to extract the full benefits of SSDs," Freeman added.

Total SSD shipments: Products take off in select apps.

Controllers help manage the read/write cycles, error correction and other functions in an SSD. But few controllers are optimized for SSD designs, said Dean Klein, VP of memory system development at Micron Technology.

Companies such as Micron, Intel, SanDisk and Samsung are developing controllers internally that they say will be optimized for SSD performance. Several merchant players, including LSI Corp., Marvell Semiconductor Inc., Silicon Motion Inc. and Phison Electronics Corp., are also developing SSD controllers that promise "increased performance characteristics with improved interfaces," Freedman said.

There are other design issues. Most of today's SSDs are based on older single-level-cell (SLC) NAND flash technology, but the ultimate goal is to develop storage subsystems based on newer, MLC NAND devices.

The limits of MLC stand as the biggest inhibitor to the growth of flash in computers. MLC offers significantly higher capacities than SLC chips. MLC chips have much higher BER, however, and can only be written about 10,000 times?one-tenth the number of cycles for single-level cell flash.

Hybrid SLC/MLC
The need for MLC-based NAND devices and controllers is "crucial" as a means to lower SSD costs, Freedman said. But the shift to MLC "puts the onus on controller makers to develop better balance between cells within a NAND device to optimize the longevity of solid-state drives," he said. "Given the pros and cons of both SLC and MLC, we believe a market for hybrid SLC/MLC exists."

With the challenges in hand, the SSD market is a moving target, Freedman added. "Like most technology introductions, we expect the introductory period to take longer than most expect, with the mass adoption period likely accelerating more rapidly than expected."

- Mark LaPedus, Rick Merritt
EE Times

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