You may have just glanced a the price for Western Digital's RE4-GP and started wondering if the pricing structure has been caught in a time warp. All is not as it seems though, because the RE4-GP line are unusual hybrids – the Caviar Green series meets an Enterprise drive, with all the power-saving of the first and reliability of the latter.

Of course, it also means extra cost, especially if you use a set of them in RAID as intended. The RE4-GP's green credentials are also part of the reason it suffers in some of our performance tests.

It employs Western Digital's IntelliPower technology, which uses less power than standard drives by reducing the spindle spin speed depending on what the drive is doing. To make up for this, the drive has a huge 64MB cache, which boosts its random access performance.

Basically, the RE4-GP 2TB is a 2TB 64MB cached Caviar Green drive with lots of added bits inside. These do little – if anything – to improve the disk's performance, but make all the difference when it comes to the drive's stability and longevity in its normal environment, which isn't in a desktop but in a server rack.

You can use it in a desktop PC, but you're paying over the odds if you do.

As well as the Western Digital power-saving Intelli technologies found in the Caviar Green (Intelliseek and IntelliPower), there's also IntelliPark, which automatically unloads the recording heads when the disk is idle and disengages the read/write channel electrics, saving even more power.

It also offers motion sensors to watch out for knocks and bumps, and is built to much tighter tolerances than much of the competition.

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