Solid state drive makers promise better power management

Update at 1:30 p.m. PDT July 3, with additional comments from Micron Technology (at bottom).

Has the image of solid state drives as power misers been shattered? A recent review would seem to dispel the notion that these devices are more power efficient than the hard disk drives used in laptops.

In an article at Tom's Hardware titled "The SSD Power Consumption Hoax", the authors state: "We have discovered that the power savings aren't there: in fact, battery runtimes actually decrease if you use a flash (solid state drive)."

(Note: Tom's Hardware has posted a correction to its original report here.)

One of the key selling points of solid state drives has been that they use less power than hard disk drives. The claim has seemed plausible because solid state drives have no moving parts, while hard disk drives have a number of moving components.

The Tom's Hardware review, however, says: "While conventional hard drives may operate at relatively low power when little movement is required...flash based drives do not. They will draw their maximum power level constantly when in use, and as a consequence, simply spend more total time drawing maximum power than conventional drives."

The review goes on to test four solid state drives (SSDs) from Crucial (Micron Technology), Memoright, Sandisk, and Mtron. For example, in evaluating the Crucial CT32GBFAB0 32GB drive, the review states, "Users who purchase this drive because of Crucial's statements such as 'low power consumption' and the product being ideal for 'users who want longer battery life' will most likely be disappointed."

Though Intel's drives were not tested in the review, the chipmaker stated Wednesday that SSDs "can be architected to improve battery life." Intel is expected to bring out drives ranging in capacity from 80GB to 160GB later this year.

Intel Fellow and Director of Storage Architecture Knut Grimsrud earlier this year presented a paper titled "Not all SSDs are Created Equal" (PDF) that stated "power efficiency must account for the amount of work being performed during the power measurement."

Whether this will actually translate into improved power efficiency when Intel brings out its drives remains to be seen.

However, high-performance solid state drive maker STEC provided some insight into what to expect. Data used in the Tom's Hardware piece applies to the current first-generation mass-market SSDs but not necessarily to upcoming drives, said Patrick Wilkison, vice president of marketing and business development at STEC. "They are using legacy drives, none of which will be used by any major PC OEM," Wilkison said in an e-mail.

Wilkison pointed out that the most competitive drives adopted by computer makers will have better power management. "Over time, these drives will need to have very intelligent power management systems. Some of these SSDs will have them, and those (that) do not have such power intelligence will not be used (by PC makers)."

And the next crop of SSDs based on multilevel cell (MLC) technology will need to aggressively manage power. "In order to make MLC viable, the drive needs a much more powerful processor/controller, which implies more power draw because frequencies will be higher, number of channels will be higher, ECC (error correcting code) engine will be working harder," he said.

STEC offers drives already with MLC technology.

Update: Micron Technology chimes in:

Micron Technology, which is a manufacturer of one of the drives used by Tom's Hardware in its review, made a statement on Thursday.

Micron will launch its next-generation RealSSD products later this year. Intel and Micron are co-partners in the joint venture IM Flash Technologies. Both companies are expected to bring out similar SSDs though they will be marketed and branded separately by the two companies.

Dean Klein, vice president of memory system development for Micron, echoed Wilkison's comments about using legacy drives in the review. He made the following statement:

"The controllers analyzed in the Tom's Hardware review are early-generation, multi-chip and in some cases even use FPGAs (field programmable gate arrays), which can be quite power hungry. As with many other first and second generation drives, these drives are not delivering on the full potential of the NAND and are not delivering properly on the performance promise.

"There is another factor to be aware of. If the CPU spends 25 million clock cycles waiting for random HDD data, but only part of that waiting for SSD data, the actual increase in notebook power consumption may be in the CPU. A useful metric is how much processing gets done per watt. If you are willing to scale back performance to that of an HDD-based system, an SSD-based system should deliver significantly longer battery life.

"Finally, consider that many of today's applications and operating systems are not optimized for SSDs, but for rotating media."