Western Digital is following up its release of its enterprise-class and consumer-friendly 10,000-rpm VelociRaptor hard drive from two years ago with two new models of even greater capacity.

Western Digital is following up its release of its enterprise-class and consumer-friendly 10,000-rpm VelociRaptor hard drive from two years ago with two new models of even greater capacity.

Whereas the first topped out at 300GB, the WD4500HLHX ($299 list) can hold up to 450GB of data, and the WD6000HLHX ($329 list) up to 600GB. Both drives are available immediately.

Like the original VelociRaptor, the 600GB version is almost two drives in one. The 2.5-inch drive is affixed to a cast metal chassis (called the "IcePack") that both functions as a heat sink and mimics the size and shape of traditional 3.5-inch hard drives so it can be used in traditional cases, cages, and racks. (Western Digital said in a statement that IcePack-less drives "are under evaluation with OEM customers and will be available through select commercial distributors within this quarter.")

Also unchanged from the VelociRaptor's original incarnation is power consumption. According to Western Digital, the 450GB and 600GB versions use no more electricity than did the 300GB incarnation: approximately 6.1 watts while reading and writing, 4.53 watts at idle, and 0.42 watts in standby and sleep modes.

There are a couple of differences between the new VelociRaptors and the previous one. Probably the most notable are that the just-released drives support the new 6-Gbps SATA interface, which may make for data transfer speeds up to 15 percent faster than could be achieved with the previous 300GB drive. An increase in cache from 16MB to 32MB will also provide another performance boost.

Particularly important for business users is an increase in reliability. Whereas the 300GB model only had a mean time between failure (MTBF) rating of 1.2 million hours, the 450GB and 600GB models are rated at 1.4 million hourswhat Western Digital calls "the highest available reliability rating on a high capacity SATA drive." The VelociRaptor drives attain this level of reliability by use of "NoTouch ramp load technology," in which the recording head never touches the disk media; this puts less wear on the recording head and offers the drive better protection when being moved. Also helpful is "Rotary Acceleration Feed Forward," which is designed to help provide optimal performance even in high-vibration environments (such as in very close proximity to a number of other fast-spinning drives).