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Power efficiency
Performance counts for a lot, but power consumption and efficiency are also important metrics to consider. In addition to looking at value purely in terms of performance, we've come up with a power efficiency rating based on the power consumption of each drive. We test each drive's power consumption under an IOMeter load consisting of 256 outstanding I/O requests with the workstation access pattern. Put that power draw in the denominator under each drive's transaction rate during that test, and you have a representation of power-efficient performance in IOps per watt. That value can then be treated like our other performance measures.

This measure may not be the most valuable one for desktop users, or even for folks considering running an SSD in their notebooks (there isn't a huge difference in power draw between most SSDs), but it's an important consideration for the sort of multi-drive arrays one might find in high-performance servers and workstations. Power consumption adds up when you're running multiple drives in RAID, and you've gotta dissipate the heat generated by every watt consumed.

Because our performance baseline is a 4,200-RPM mobile drive, the baseline power consumption is quite low. Even with dismal performance, the ancient Travelstar still scores higher on the IOps-per-watt scale than the Caviar Black, which consumes several times more wattage. Rather than switching baselines, we've simply left the Black out of these results.

We shouldn't be surprised by the strong showing of the SandForce drives here. After all, they do offer the highest IOMeter transaction rates. Their power consumption is also quite competitive with that of the other SSDs.

Interestingly, a number of SSDs score quite poorly here. The Scorpio Blue and SSDNow have painfully low IOMeter transaction rates to begin with, so their low power consumption is of little help. Conversely, it's the relatively high power consumption of the Intel SSDs that hurts their standing on our efficiency scale.

If you discount the SandForce SSDs, the RealSSD and Nova are the next two in line. The C300 pushes more IOps at a lower cost per gigabyte.