Power Consumption

You can refer to our article called Hard Disk Drive Power Consumption Measurements: X-bit’s Methodology Indepth for details on this test. We’ll just list the specific modes we measure the power consumption in:

• Start (the current the drive consumes when speeding up its spindle)
• Idle (the drive is not accessed at all, but it is turned on and ready to work)
• Random Read and Write
• Sequential Read and Write

Let's take a look at each mode individually:

We used to criticize Western Digital for the aggressive spinning-up of the platters in its products. Yes, the company’s HDDs would spin up faster than opponents, but required such a high current that many users had problems powering them via USB. We can remind you that the maximum current through a USB connector is 0.5A (although specific mainboards can provide more). Thus, a HDD can get only 1 ampere from two USB ports.

It is good that Western Digital has thought about that problem: while the 320GB model consumes more than 1 ampere at startup, the 500GB model is the most economical in this review. The Samsung is economical, too. The 3-platter Hitachi needs a little more than 1 ampere, so you can have problems powering it from USB ports.

When not accessed, three of the four HDDs deliver similar results and require less than 1W of power. The Samsung is somewhat worse than the others here.

Take note that today’s drives do not spend much power for keeping their platters running. The Hitachi needs about the same amount of power for its three platters as the others for two.

Random writing requires less power in comparison with reading. The higher consumption of the electronics at writing seems to be made up for by the deferred writing algorithms in each drive.

The new 500GB Western Digital is overall somewhat more economical than its 320GB predecessor. The difference is 0.28W at both writing and reading. This does not look like a lot, yet amounts to about 10%. It is especially good that the new Scorpio is the only drive to require less than 2.5W (the maximum amount of power provided by a single USB port).

As for the other participating devices, the 2-platter Samsung needs somewhat more power than the 3-platter Hitachi. Easy to guess, this depends on the power consumption of the drive’s actuator.

It is at sequential operations that a HDD usually has its highest power consumption because both the heads and the electronics are working at their full capacity. This test is an example of that. Take note that the HDDs generally need more power at writing and at reading. This is due to the electronics’ caching requests while there is no opportunity for request optimization.

And again the 500GB Western Digital deserves our praise. While the previous model was very hungry, the newer model almost fits within 2.5W, catching up with the very economical Hitachi. The Samsung is voracious. Its electronics seems to be not optimized in terms of power efficiency.

By the way, all the power the hard disk drive consumes at work transforms into heat in its electronics or mechanics. Thus, the power consumption data are indicative of how much power the HDDs dissipate. The most economical HDDs are also going to be the coolest.