When we looked at Western Digital's "GreenPower" Caviar GP last month, we heralded the drive's low noise levels and frugal power consumption. Given the GP's slower spindle speed and energy-efficient billing, those results were largely expected. What surprised us, however, was how well the GreenPower Caviar handled demanding multi-user loads. It's not often that you find low power consumption with strong performance riding shotgun.
That combination makes the GreenPower drives particularly enticing for enterprise environments looking to maximize storage capacity within a limited power budget. Don't think that potential went unnoticed at Western Digital. The company has been massaging the GP to better suit enterprise applications, and the result of those efforts is the new RE2-GP.
As one might expect, the RE2-GP has much in common with the Caviar GP. However, the RE2 packs a few additional perks, including a longer warranty, optimization for RAID environments, and firmware tweaks that aim to deliver better performance with enterprise-class applications. Read on to see how those firmware tweaks affect the GreenPower's performance and why this drive might be a slam-dunk for enterprise storage.
Tweaked for enterprise
"IntelliPower" lies at the core of the GreenPower line, a marketing name that signifies a delicate balance of transfer rate, cache size, and spindle speed that ensures low power consumption along with what Western Digital calls "solid" performance. Two of the RE2-GP's IntelliPower key specs are easy to pin down: the drive has 16MB of cache, and its spec sheet boasts sustained transfer rates of 672Mbps, or 84MB/s. However, the third and arguably most important element—spindle speed—remains shrouded in mystery.
Western Digital won't reveal the exact spindle speed of its GreenPower drives, saying only that they run somewhere between 5,400 and 7,200 RPM. Spindle speeds vary depending on capacities, too, although all GP drives at a given capacity run at the same speed. We've also confirmed that RE2-GP drives share the same spindle speeds as their like-capacity Caviar GP counterparts.
|Maximum external transfer rate||300MB/s||300MB/s|
|Maximum buffer to disk transfer rate||1,156Mbps||NA|
|Sustained buffer to disk transfer rate||NA||672Mbps|
|Read seek time||8.9ms||8.9ms|
|Write seek time||NA||NA|
|Average rotational latency||5.6ms||NA|
|Idle power consumption||4.0W||4.0W|
|Read/write power consumption||9.5W||7.4W|
|Native Command Queuing||Yes||Yes|
|Warranty length||Three years||Five years|
Spindle speed factors heavily in overall drive performance, so it's disappointing the GreenPower spec sheets aren't more forthcoming. That's not the only factor in the performance equation, though. Areal density also plays a major role, and in that respect the RE2-GP is well-equipped, with the same 250GB platters as the Caviar GP. These relatively high density platters allow the drive head to access data over shorter physical distances, helping to offset the GP's slower spindle speed.
We'll see just how well a high platter density can mask the performance impact of a lower spindle speed in a moment, but first, it's important to highlight why Western Digital opted to turn down the GreenPower's spindle speed in the first place. As one might expect, slower spindle speeds require less juice, giving GreenPowers lower rated power consumption than any other terabyte drives on the market. This reduction in power consumption is a nice perk for the Caviar GP, but it's an even bigger boon to the RE2-GP, which is likely to be deployed in multi-drive environments where power savings can really add up. In fact, Western Digital is so keen to push the RE2-GP's power efficiency in multi-drive environments that it's cooked up a web-based power consumption calculator to help prospective customers quantify the potential savings.
Despite being targeted at very different environments, the Caviar GP and RE2-GP are actually mechanically identical. The drives share similar feature sets, too, including support for an IntelliPark mechanism that moves the drive heads off the media at idle to reduce aerodynamic drag. WD's IntelliSeek just-in-time actuator delivery scheme is also under the hood, taking advantage of the rotational latency inherent to spinning media by only moving the drive head as fast as necessary—rather than as fast as possible—to get it into position for the next data point. WD also deploys a StableTrac motor in the 750GB and 1TB flavors of the RE2-GP, which secures its
bad self shaft at both ends rather than just one.
The RE2-GP comes with a few features missing from the Caviar GP. These RAID-specific optimizations include Rotary Acceleration Feed Forward (RAFF), which detects and compensates for the ambient vibrations typical of multi-drive environments, and Time-Limited Error Recovery (TLER), which restricts the amount of time a drive will attempt solo error recovery, lest it be dropped from a RAID array for being unresponsive for too long. Heroic as they may be, prolonged error recovery attempts are unnecessary in RAID environments, since RAID controllers prefer to handle error recovery on their own.Western Digital also provides additional validation testing for its enterprise-class drives, and although the RE2-GP isn't necessarily more reliable than its desktop counterpart, the drive benefits from two more years of warranty coverage. That won't guarantee the safety of your data for an additional two years, but with the RE2-GP, you should have a RAID array ensuring redundancy anyway.
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