The latest PC component to undergo a power-efficiency makeover is one we weren't quite expecting: the hard drive. Western Digital's latest Caviar SE16 features IntelliSeek, a just-in-time approach to actuator movement that is supposed to not only lower power consumption but also reduce noise levels by minimizing seek-induced vibration. WD claims these gains are accomplished without slowing seek times, which bodes well for the Caviar's appeal among enthusiasts who demand that power savings not come at the expense of performance.
Western Digital has also given the drive a much-needed capacity boost up to 750GB courtesy of four perpendicular-packed platters, and they've fiddled with the internals to improve reliability. Are those changes, coupled with IntelliSeek, enough to elevate the Caviar above its rivals? Read on to find out.
The latest Caviar's 750GB capacity is a 50% boost for Western Digital, whose drives have topped out at 500GB for some time now. However, the Caviar is far from the first drive to break the 500GB barrier. Hitachi's terabyte Deskstar is finally starting to pop up at online retailers, and Seagate has offered 750GB flavors of its Barracuda 7200.10 for more than a year now.
At first glance, Western Digital's stab at the 750GB mark closely follows Seagate's lead. The 750GB Barracuda 7200.10 achieved its then-industry-leading capacity using four 188GB platters and perpendicular recording technology, and this latest Caviar SE16 does the same. Both drives also feature 16MB of cache and 7,200-RPM spindle speeds. That's where the similarities end, or at least where they become difficult to compare. Hard drive manufacturers can't seem to agree on a collection of consistent specifications to publish, so we're left comparing the 750GB Caviar SE16—model number WD7500AAKS—to its 500GB predecessor, the WD5000KS.
|Maximum external transfer rate||300MB/s||300MB/s|
|Buffer to disk transfer rate||972Mbps||748Mbps|
|Read seek time||8.9ms||8.9ms|
|Write seek time||10.9ms||10.9ms|
|Average rotational latency||4.2ms||4.2ms|
|Idle power consumption||8.40W||8.75W|
|Read/write power consumption||8.77W||9.5W|
|Native Command Queuing||Yes||Yes|
|Warranty length||Three years (OEM)|
One year (Retail)
|Three years (OEM)|
One year (Retail)
As you can see, the new Caviar doesn't improve on its predecessor's 300MB/s Serial ATA interface or spindle speed. Internal transfer rates are much faster for the 750GB drive thanks to the higher areal density of its platters, though. Higher areal densities lead to faster transfer rates by allowing the drive head to access more data over the same physical distance. Western Digital employs perpendicular recording technology to squeeze 188GB onto each of the new Caviar's four platters, where the 500GB model is stuck with only 125GB per platter using older longitudinal recording tech.
While the 750GB Caviar has a transfer rate advantage over its predecessor, seek times are unchanged. How the drive goes about seek operations is different, though. In traditional hard drives, the actuator rapidly accelerates the drive head to the location of the next data point, regardless of when that data point will actually be in position to access. Because data points are located on a spinning platter, it may take milliseconds—a virtual eternity within the confines of a modern PC—for the target to come 'round. Western Digital takes advantage of this rotational latency with an IntelliSeek mechanism that only moves the actuator as fast as necessary to get it into position for the data point's next arrival.
IntelliSeek is best thought of as just-in-time actuator movement. The drive head will always move fast enough to be in position to access the next data point, but if that point isn't due for a few milliseconds, the actuator will take its time getting there. Western Digital says this approach conserves power and reduces noise and vibration compared with traditional actuators that mindlessly dart from data point to data point, and they're adamant that performance isn't sacrificed. You can see an animated representation of IntelliSeek in action on Western Digital's website here.
In addition to outfitting the 750GB Caviar with a more intelligent approach to seeking, Western Digital has equipped the drive with a StableTrac motor that secures the shaft at both ends. According to Western Digital, this arrangement helps the drive deal with environmental vibration that could be induced by particularly loud music or the far-too-common practice of putting a subwoofer right next to a PC. The Caviar also borrows a SecurePark mechanism from Western Digital's mobile group that parks the drive head off the disk when the drive is powered down, during spin-up and, during spin-down. This feature increases the drive's tolerance of non-operational shock, and Western Digital adds that it can reduce the creation of microparticles during spin-up and spin-down, increasing the reliability of the drive.
Despite its apparently improved reliability, the Caviar SE16 750GB's warranty coverage is limited to either one or three years, depending on how you buy the drive. Somewhat counter-intuitively, retail drive kits are only covered for a single year, with three years of coverage limited to bare drives. That discrepancy is odd, but since enthusiasts typically buy bare drives, we're getting the better end of the deal.
However, even a three-year warranty looks a little stingy next to the five years of coverage you get with any of Seagate's hard drives and with Western Digital's own enterprise-class products. When asked why it hasn't expanded its five-year warranty to include desktop products, Western Digital told us the additional cost just isn't worth it. Bare drives make up a very small percentage of the market, they say, and the additional overhead and bookkeeping costs associated with longer warranty periods is substantial. Western Digital also claims that its drives have very low failure rates between years three and five. Western Digital is working on an enterprise-class version of this latest Caviar, though, and that drive should carry a five-year warranty.
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