If PC enthusiasts had a hall of fame for hardware, Western Digital's Raptor hard drive would be a shoo-in. Storage-related products are usually a little short on sex appeal, but the Raptor has become an icon—a testament to what it means to be an enthusiast.

Like many enthusiast legends, the Raptor started with enterprise-class hardware designed for corporate server rooms. Western Digital, a plucky desktop drive maker with no answer to the SCSI hardware that dominated the enterprise scene at the time, came to bat with the world's first 10K-RPM Serial ATA hard drive. The original Raptor didn't usurp the enterprise crown from well-established SCSI players, but its performance blew away every other Serial ATA hard drive on the market. What's more, the Raptor plugged into standard desktop motherboards, delivering near-SCSI performance without the need for expensive expansion cards.

Enthusiasts were so hungry for the performance delivered by the Raptor's 10K-RPM spindle speeds that we were willing to live with the drive's anemic 36GB capacity. That capacity slowly grew over time, with Western Digital upping the Raptor to 74GB in 2004 and 150GB two years later. The Raptor's last refresh was a couple of years ago, though, and the drive has fallen behind a new wave of terabyte wonders whose crazy-high areal densities deliver phenomenal performance even at 7,200 RPM.

Western Digital wasn't about to let a performance icon get beaten by run-of-the-mill desktop drives, and certainly not by ones manufactured by companies that also make washing machines, so they've rolled out an all-new Raptor. Specifically targeted at enthusiasts, the VelociRaptor VR150 breaks bold new ground by bringing 10K-RPM spindle speeds to a 2.5" drive buried inside a heatsink that slides into a standard 3.5" drive bay. Read on to see why this is a brilliantly ambitious idea and whether it allows the VelociRaptor to reclaim the crown of fastest Serial ATA hard drive on the market.

The rationale for a 2.5" Raptor
Although it's technically correct that the VelociRaptor is the world's first 2.5" Serial ATA drive with a 10K-RPM spindle speed, it's not the first 2.5" drive to spin its platters that fast. Seagate's Savvio did it first, albeit with a SCSI interface. Savvios are aimed squarely at enterprise environments where the ability to pack more drives into rack-mounted servers can pay huge dividends.

The benefits of a 2.5" form factor go beyond drive density, though. Smaller platters give the drive head a much smaller area to cover. The jump from the innermost track of a 2.5" platter to the outermost track is much smaller than it is for a 3.5" platter. As a result, 2.5" drives have an inherent edge in seek times and random access patterns. That said, 2.5" drives are at somewhat of a disadvantage in a straight-line drag race. Here, the fact that 2.5" drives have a much smaller circumference on their outer tracks—the fastest area of the disk for sequential transfers—can be a hindrance.

Power consumption has become an increasingly important consideration, and 2.5" drives have an advantage there, as well. Smaller platters are lighter, allowing the drive motor to draw less power. Making life easier on the drive motor can enable 2.5" drives to run quieter than their 3.5" counterparts, too.

So the prospect of a 2.5" Raptor sounds promising. But the form factor is a bit of a liability for enthusiasts, because standard desktop enclosures don't come with bays designed for 2.5" hard drives. To get around this issue, Western Digital slips the 2.5" VelociRaptor into an "IcePAK" drive sled that neatly slides into standard 3.5" drive bays. The IcePAK is equipped with 13 cooling fins, providing additional surface area for its secondary task: acting as the VelociRaptor's heatsink.

Western Digital says 2.5" 10K-RPM drives don't necessarily require heatsinks, but they do run warmer than standard desktop drives. The VelociRaptor needed an adapter to be compatible with 3.5" drive bays anyway, so having one that serves as a heatsink is a simple but smart bit of engineering.

It sounds like Western Digital has worked out all the angles for the VelociRaptor, but the fact remains that bringing 10K-RPM spindle speeds down to a 2.5" form factor is no easy task. 2.5" drives are just really tiny—the actual drive that sits inside the VelociRaptor's IcePAK sled is roughly 70% smaller by volume than a standard 3.5" drive—and it's difficult to pull off miniaturization while maintaining breakneck spindle speeds.

To be fair, though, the 2.5" drive at the heart of the VelociRaptor isn't quite as small as a common notebook drives. The 2.5" form factor standard has provisions for different drive thicknesses, with most of today's notebook drives conforming to the thinnest 9mm option. The VelociRaptor's 2.5" drive measures 15mm thick, which means you won't be able to squeeze it into a standard notebook. The VelociRaptor's thickness neatly matches that of Seagate's Savvio drives, though.

Given its form factor, the VelociRaptor's core seems like a logical and potentially very attractive Serial ATA alternative to Seagate's Savvio drives in the enterprise world. However, Western Digital isn't talking about an enterprise version of the VelociRaptor just yet. Enthusiasts get first dibs this time around.