Good Gear Guide
Western Digital VelociRaptor: 10K spin speed for w...
The striking design of the VelociRaptor is actually critical to the drive's performance: its small platters have a density of 150GB each, and they spin at 10,000rpm, so the heads can access more data over a shorter distance than most drives. With two platters installed, the VelociRaptor has a total capacity of 300GB. And while the drive itself is approximately the size of a notebook hard drive, it won't actually fit into a notebook as it's a little bit thicker (15mm) than a standard notebook drive. Not only that, but it requires 12V to run, whereas typical notebook drives are 5V.
Western Digital VelociRaptor: 10K spin speed for workstations and gaming PCs