What gets sacrified to get a green hard drive

Days after the Environmental Protection Agency launched its Energy Star 4.0 , the energy-savings initiatives are flowing in. Western Digital threw itself into the ring with the announcement of its Caviar GreenPower hard disk drives.

According to Western Digital, the impetus for change began with Climate Savers Computing Initiative, a consortium of technology companies who’ve banded together to reduce the PC’s power consumption by 50 percent by the year 2010. The group was started this year by Google and Intel.

“When you’re talking about those kinds of cuts, you have to go beyond just the CPU and power supply; you have to get into the storage side, too,” explains Ted Deffenbaugh, director of product marketing for desktop drives at Western Digital.

The company began exploring ways to reduce power consumption in mobile and particularly desktop drives. The result of its program: Dropping power consumption by up to 38 percent with the new GreenPower drives. Western Digital has been able to go from 13 watts during operation–on its own drives as well as competitors’ drives–to just 8 watts.

To achieve such a dramatic power cut, Western Digital had to rethink the drive’s design–as well as rethink the goals of a new hard drive. “It’s always been about more speed, never about doing what we’ve been doing with less power,” admits Deffenbaugh.

The question isn’t really if you will sacrifice something to gain green-friendly status; the question is what you will sacrifice, and how much? Western Digital says it has approached the issue pragmatically, to strike a balance the company deems an appropriate compromise. “We set an acceptable bar for performance,” Deffenbaugh explains. “And then we worked as hard as we could to lower power in the overall drive, by starting to tune back on some parameters.” Those parameters include adjusting the rotational speed, using bigger data buffers, parking the drive’s head, and optimizing how the drive seeks and caches data.

Of those, reducing the rotational speed will have the greatest direct impact on a drive’s performance. Desktop, 3.5-inch hard drives today typically spin at 7200 rpm. On the Caviar GP drives, Western Digital says that it’s setting a unique rotational speed for the drives. “Depending upon the capacity, our benchmarking, and our mathematical modeling, we are going to spin these drives at a speed between 5400 and 7200 rpm,” says Deffenbaugh.

The speed will be fixed at any given capacity. “We will set an rpm that we think balances the performance vs. the power savings. Our goal is to have these drives perform the same as a Seagate drive with an 8MB cache.”

The other area Western Digital has worked on is reducing the workload of the drive. The company has addressed this in two ways. The first is through what it calls its IntelliPark capability, new to the Caviar GP drive. IntelliPark represents a morph of Western Digital’s SecurePark, a technology for pulling the head off the disk and locking it.

“When the drive is just spinning, and not doing reading and writing–times when the drive light is not flashing–we anticipate the type of workload that is being generated, and we can pull the head up and off the disk. Now,” says Deffenbaugh, “we took our mechanism and through software, we added intelligence about when to pull the head off the disk.” That, in turn, translates into power savings by lowering the drag on the disk dramatically. “That’s one of the ways we can drop power when the drive is not actively seeking or reading data.”

The third tactic is a technology Western Digital has dubbed IntelliSeek. This technology takes advantage of the drive’s integrated native command queuing to do fewer random seeks, which in turn lowers power consumption.

All of these changes have led to other benefits, too: The new Caviar GP drives are less noisy than previous models–shaving 5 decibels from the noise level. And operating temperature has been lowered as well.

While the Caviar GP drives won’t be the company’s fastest performers, Deffenbaugh says he doesn’t expect the performance hit to be as big you as might expect. “We can make up some of the performance gap by being clever how we do our microcode operating system in the hard drive itself, and in how we do caching.” Also, he notes, improved use of native command queuing–which requires drive, operating system, and application support–will help compensate for having a lower rotational speed.

The first Caviar GP drives will show up inside Western Digital’s own external drives. Announced Tuesday, the 2TB My Book dual-drive models–My Book World Edition II, My Book Pro Edition II, My Book Premium Edition II–will feature the 1TB Caviar GP inside. Internal Caviar GP drives will ship in the second or third week of August.

Pricing will be in line with what you expect from a standard drive. Says Deffenbaugh, “The strategy on the Caviar GP is to use the line for [growing] market share, not for enhanced profitability.”