WD Green Power: A New Benchmark in HDD Acoustics & Power

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TEST RESULTS

Our sample was tested according to our standard hard drive testing methodology. Our methodology focuses specifically on HDD noise, and great effort is taken to ensure it is comprehensively measured and described. Performance is not tested, for reasons discussed in detail in the methodology article. For comprehensive HDD performance testing results, we recommend Storage Review, who have established a long reputation as the specialist in this field. Their review of the Western Digital Green Power can be found in a roundup of several terabyte drives.

Our test drive was compared against our reference drives, the Seagate Barracuda IV and Samsung Spinpoint P80, which are profiled in our methodology article. To get a good idea of where the drives in this review stand, it is important to read the methodology article thoroughly. It was also compared against our current low-noise champ: A 500 GB Western Digital WD5000KS. A 250 GB Spinpoint P120 was also included in the comparison.

Two forms of hard drive noise are measured:

  1. Airborne acoustics
  2. Vibration-induced noise.

These two types of noise impact the subjective perception of hard drive noise differently depending on how and where the drive is mounted.

Both forms of noise are evaluated objectively and subjectively. Both the subjective and objective analyses are essential to understanding the acoustics of the drives. Airborne acoustics are measured using a professional caliber SLM. Measurements are taken at a distance of one meter above the top of the drive using an A-weighted filter. Vibration noise is rated on a scale of 1-10 by comparing against our standard reference drives.

A final caveat: As with most reviews, our comments are relevant to the sample we tested. Your sample may not be identical. There are always some sample variances, and manufacturers also make changes without telling everyone.

Ambient conditions at the time of testing were 18 dBA and 20°C.

DRIVE NOISE EVALUATION
Drive
Mfg date
firmware version
Vibration
1-10
(10 is best)
Activity State
Airborne Acoustics
Measured Power
Western Digital Caviar Green Power WD7500AACS
October 2007
firmware 01.01B01
7
Idle
19~20 dBA@1m
3.3~5.9 W
Seek (AAM)
19~20 dBA@1m
5.4 W
Seek (Normal)
21 dBA@1m
6.7 W
REFERENCE DRIVES
Western Digital Caviar SE16 WD5000KS
March 2006
firmware 07.02E07
4
Idle
21 dBA@1m
8.5 W
Seek (AAM)
21-22 dBA@1m
8.6 W
Seek (Normal)
23 dBA@1m
10.7 W
Seagate Barracuda IV
ST340016A - firmware 3.10
6
Idle
20 dBA@1m
6.7 W
Seek (AAM)
23 dBA@1m
11.3 W
Seek (Normal)
25-26 dBA@1m
11.6 W
Samsung Spinpoint
P120 SP2504C

September 05 - firmware VT100-33
5
Idle
21 dBA@1m
7.2 W
Seek (AAM)
23-24 dBA@1m
9.4 W
Seek (Normal)
23-24 dBA@1m
10.3 W
Samsung Spinpoint P80 (Nidec motor)
June 04 - firmware TK100-24
4
Idle
21 dBA@1m
6.3 W
Seek (AAM)
23-24 dBA@1m
8.3 W
Seek (Normal)
25-26 dBA@1m
9.1 W
Samsung Spinpoint P80 (JVC motor)
Feb 05 - firmware TK200-04
6
Idle
21 dBA@1m
6.2 W
Seek (AAM)
25 dBA@1m
n / a
Seek (Normal)
27 dBA@1m
9.3 W

Ladies and Gentlemen, the numbers don't lie: This is the quietest desktop drive we've ever tested. Well — sometimes they do, but not this time; subjectively, the drive was just as quiet as its barely-above-ambient objective results suggest. The biggest difference? A large reduction in air noise. It makes sense — just like a fan, a slower-spinning drive produces less air turbulence, which means less noise. The lower amount of air noise uncovered a faint trace of electronic noise, but this was not audible from a distance, and it would disappear entirely inside a system.

Seeks were soft, low, and measured very well. However, they were slightly more obvious than the last Western Digital we looked at — mainly because the seeks on that drive disappeared under the whoosh of air noise. Without this broadband noise, the seeks on the Green Power were clearly audible once more. That said, measurement for AAM seeks was indistinguishable from the idle measurement, so there's no question they are quiet. Any fan running above ~700 RPM should generate enough noise to cover the seek noise completely.

Besides idle and seek noise, the Green Power produced one more noise: A pair of sharp clicks whenever the heads were loaded or unloaded (that is, whenever the drive went into or came out of idle mode). This noise was louder than the similar noise made by most notebook drives, but quieter than the infamous head reset noise made by certain Hitachi models. The noise was quite similar to seek noise and was roughly the same volume. On close listening, it seemed slightly sharper than the seek noise.

In addition to low direct noise, the Green Power also tied the best (that is, lowest) vibration of any desktop drive we've tested. Once again, the lower rotation speed can be credited. Not only does the lower speed translate into less momentum, but the resonant frequency is lower and thus harder to hear. On our highly resonant aluminum test box, the drive produced just enough hum to have a presence, but it was difficult to pick out the hum on its own. In a real system, it would be unlikely to be heard at all.

With such good measurements, we were curious to see how the Green Power stacked up against the legendary Barracuda IV. This drive has stood as the quietest desktop drive ever since we first saw it, though it has been obsolete for years. The verdict? The Green Power had slightly more air noise, but it lacked the slight whine that the Barracuda IV's exhibited. Of the two, the air noise was slightly easier to ignore, but it's not a huge advantage either way. Seek noise, on the other hand, was squarely in favor of the Green Power. The Barracuda IV had short, staccato seeks that drew attention to themselves with their suddenness. The Green Power sounded far more relaxed (as well as being quieter overall), and the rumble of the seeks blended easily into the background.

The Green Power's biggest claim to fame is power consumption, and our measurements confirmed its efficiency. Measuring the power at idle proved difficult, since the drive appeared to cycle certain functions on and off apparently at random, so the power consumption rarely stayed the same for more than a few seconds. During our measurements, we observed everything from 3.3W to 5.9W at idle, but the most common level was 3.7W when the heads were unloaded. This is by far the most efficient drive we've tested, with the next-closest competitor being a 160 GB model from Hitachi, at 4.7W. Seek power was similarly frugal, with no other drives coming close.

Western Digital's estimate of a 40% power savings actually seems a little conservative on the basis of the drives we've tested, as the Green Power actually drew less than half the power of some of the drives in our database. This was true no matter what state the drives were in.



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