Back in the 70s, Kermit the frog lamented that it wasn't easy being green. My, how times have changed. In this new millennium, being green isn't only easy, it's practically expected. Neighbors sneer if you put out more garbage than carefully washed and sorted empties for recycling; grocery stores rake in what I can only assume are huge profits charging five cents per plastic bag; and those who carpool are rewarded with their own special lanes to bypass traffic congestion. Who can blame us, with the inventor of the Internet predicting that melting polar ice caps will one day force us to relive Waterworld.

This push toward environmental friendliness has even permeated the PC industry. Most new components comply with the Restriction of Hazardous Substances (RoHS) directive, for example. The recent trend toward lowering power consumption and improving energy efficiency also lends itself to hugging the planet, even if it was mostly inspired by a desire to reduce the noise generated by Prescott heatsinks.

There's no ulterior motive behind the latest component to hop on the green bandwagon, though. Western Digital's new Caviar GP hard drive breaks new ground as the first desktop drive we've seen designed explicitly to lower power consumption. Energy efficiency isn't new in the hard drive world, of course; mobile drives have carefully sipped power to conserve notebook battery life for years. However, the Caviar GP is a 3.5" drive meant for desktops, and that makes it rather special.

There's more to the Caviar GP than its Birkenstocks, too. The drive packs a mind-bending 250GB per platter and is available in capacities up to a cool terabyte, making it the biggest drive in the Caviar line. There's a catch, of course. While most desktop drives spin at either 5,400 or 7,200RPM, the Caviar GP's spindle speed lies somewhere between the two, and Western Digital won't say exactly where.

With its spindle speed shrouded in mystery, we couldn't help but wonder whether the Caviar GP's performance leans more toward the Tesla Roadster or the Toyota Prius. And what does a slower spindle speed mean for power consumption and noise levels? To find out, we've tested the drive against 20 others, with surprising results.

The drive
The fact we don't know the Caviar GP's spindle speed is unusual enough, but it only gets more complicated from there. You see, although Western Digital won't reveal the GreenPower's exact spindle speed, they did tell us that it varies depending on capacity. The GP is available in capacities of 500GB, 750GB, and 1TB, each of which has a different spindle speed designed to maximize the drive's overall energy efficiency.

And there's more.

The GP's spindle speed falls under an "IntelliPower" umbrella that also includes the drive's transfer rate and cache size. Western Digital says these three elements are massaged to "deliver significant power savings and solid performance." Yet spindle speed appears to be the only part of the IntelliPower equation that actually varies depending on drive capacity. GreenPower drives at 500 and 750GB list the same transfer rate and cache size as the 1TB model we're looking at today.

Differences in spindle speed ensure that Caviar GP performance will depend on capacity. Since we're testing the terabyte GreenPower, we'll limit our discussion to that model from here forward.

Squeezing a terabyte into a 3.5" hard drive form factor is no easy task, but Western Digital has done it in style using platters that offer a much higher areal density than its other drives. The Caviar GP makes use of perpendicular recording techniques similar to those used by the Caviar SE16 and RE2. Those drives only manage to pack 188GB per platter, though, while the GP shoehorns 250GB onto each disk.

Higher density platters can improve performance by allowing the drive head to access more data over shorter physical distances. This effect is evident when we look at the GP's maximum buffer-to-disk transfer rate, which is nearly 200Mbps faster than that of the Caviar SE16, despite the drive's sub-7,200-RPM spindle speed.

Although the Caviar GP spins a little slower than its SE16 and RE2 cousins, the drive's average read seek time is every bit as fast. Don't get too excited, though. Western Digital doesn't publish the GP's write seek time. WD does list the drive's rotational latency, and it's quite a bit slower than the RE2 and SE16.

Average rotational latency refers to half the time it takes for a disk to complete one revolution, and with a little simple arithmetic, it's easy to convert that to revolutions per minute, or RPM. 5.6 milliseconds of rotational latency works out to about 5,400 RPM, which just happens to be the low end of the GreenPower's spindle speed range. Western Digital says that's by design; the latency spec it lists in the GreenPower's data sheets is merely an estimate based on the spindle speed range of the drive. So much for sleuthing.

We've been fussing over spindle speeds so much because they play a major role in determining drive performance. But the Caviar GP isn't meant to ride the bleeding edge of performance; it's supposed to be quiet and efficient, and the drive's specs bear that out. Western Digital rates the GP as quieter than either the Caviar SE16 or RE2 at idle and under load. Power consumption is lower, as well. Even with its terabyte capacity, the GreenPower drive requires just four watts at idle—half that of its 750GB cousins. Curiously, though, the GP's read/write power consumption is actually a little higher than that of the Caviar SE16.

The Caviar SE16 is, of course, a particularly energy-efficient 7,200-RPM drive. Among its power saving features is a little something called IntelliSeek—a just-in-time actuator delivery scheme that conserves power by allowing the drive to move the head only as fast as is needed to get it into position for the next data point. IntelliSeek can also be found inside the Caviar GP alongside a mechanism called IntelliPark. According to Western Digital, IntelliPark unloads idle drive heads to reduce aerodynamic drag, in turn reducing the amount of energy required to spin the platters. The Caviar GP also features WD's StableTrac motor, which secures the motor shaft at both ends to reduce vibration. StableTrac is only available on 750GB and 1TB GreenPower models, though.

Warranty coverage is consistent across all three Caviar GP capacities at three years. Naturally, we'd prefer to see the GP inherit the five-year warranty lavished upon enterprise-oriented drives like the RE2. That wouldn't necessarily make the GP more reliable, but it would entitle you to a replacement drive in the event of a hardware failure for an additional two years. Thus far, only Seagate has stepped up to the plate and offered five years of warranty coverage on its standard desktop drives.