Solid-state disk lackluster for laptops, PCs

Computerworld - Most observers agree that solid-state disk (SSD) will eventually overtake magnetic disk drives as the storage medium of choice. SSD is lighter than traditional hard disk drives, is faster, is more durable and consumes less power. Still, SSD doesn't measure up to the hype, particularly when using it in a desktop or laptop PC.

"There are a host of problems with SSD," says Avi Cohen, head of research at Avian Securities LLC in Boston. "There's no reason to pay the extra $600 to $800 -- or a 40% to 80% premium -- for a solid-state drive."

Cohen is not alone in his assessment of consumer-grade SSD. Consumer-grade SSD generally uses multilevel cell (MLC) NAND flash memory, which has greater capacity and a lower-price point but suffers from slower I/O and as much as 10 times fewer read/writes over its life span. Corporate-grade SSD uses single-level cell (SLC) NAND memory and multiple channels to increase data throughput and wear-leveling software to ensure data is distributed evenly in the drive rather than wearing out one group of cells over another. And, while some consumer-grade SSD is just now beginning to incorporate the latter features to increase its performance, there will still be a cost/capacity disparity for years to come.

Other analysts agree, and even disk drive makers, including Fujitsu Ltd., do not see themselves producing SSD for at least another two years. That's how long it will take before the cost-vs.-benefit ratio makes sense for SSD to be a viable alternative to hard disk drives in laptops and PCs.

"I think you need to get to 128GB for around $200, and that's going to happen around 2010. Also, the industry needs to effectively communicate why consumers or enterprise users should pay more for less storage," says Joseph Unsworth, an analyst at Gartner Inc., referring to the fact that a 1TB hard disk drive today can cost under $200. A 1TB SSD would cost tens of thousands of dollars, he says.

Today, consumer-grade SSD costs from $2 to $3.45 per gigabyte, hard drives about $0.38 per gigabyte, according to Gartner and iSuppli Corp. Just two years ago, SSD cost $17.50 per gigabyte, so it's obvious that consumer NAND flash memory will soon be a true contender to hard disk drives -- it's just not there yet.

"As a percentage of the whole solid-state drive industry, it'll remain pretty light for now," says Joel Hagberg, Fujitsu's vice president of business development. "Pricing needs to get better."

Intel Corp.'s and Micron Technology Inc.'s upcoming SSDs will be based on 32Gbit chip technology. The companies are expected to be the first to break the $1.00 a gigabyte barrier with their upcoming consumer SSD products, which will cost about $0.99 cents a gigabyte, according to Jim Handy, an analyst at Objective Analysis.

How SSD works

Two types of NAND flash memory are used to make SSD: SLC, storing one bit per cell and MLC, storing two or more bits per cell. Even without any software or firmware enhancements, SLC memory is inherently faster, is more reliable and has greater longevity than MLC, Avian Security's Cohen says. On the other hand, SLC is also more costly to produce and stores significantly less data than MLC.

All SSD natively excels at sequential and random reads -- such as watching videos or listening to music -- because as long as there's free space, the operations require no additional processing to retrieve data. This is why SSD is an excellent choice for handhelds; these devices are used mostly to access music or video, with few data writes required.

NAND is not efficient at random writes. In fact, most vendors tout burst speeds when offering read and write rates without showing sustained sequential figures in their marketing materials, according to Cohen, Unsworth and others. To make up for this shortcoming, vendors are trying to navigate slow read/write speeds not through the NAND flash itself, but through the controller electronics, memory buffers, multiple controller channels, interleaving NAND chips in parallel and flash management software, according to Unsworth.

For example, this month Micron unveiled its newest SSD line for notebooks, the C100 and C200 models, which have from 32GB to 128GB of capacity. Micron states that the drives offer sustained read speeds of up to 250MB/sec. and write speeds of up to 100MB/sec.