Confirming last week's speculation, Seagate has unveiled a hybrid mechanical and solid-state drive, uniting the best of both realms: speed and affordability. The 2.5-inch Momentus XT is available in 250GB, 320GB and 500GB capacities, and has 4GB of SLC NAND flash memory onboard. The drive features what Seagate calls "Adaptive Memory," which automatically moves frequently accessed data to the flash memory, thus allowing the Momentus XT to outpace standard platter drives.

Although Seagate's new drive isn't quite as fast as most SSDs, it's unfair to expect such performance. Rather than see the Momentus XT as a slow SSD, it makes more sense to view it as a fast HDD – and fast it is. In AnandTech's testing, the drive performed like a quieter, less power-hungry VelociRaptor (Western Digital's 10,000RPM units). Momentus XT drives are up for preorder via Amazon for $107, $115, and $137 – a bit more than mechanical notebook drives sans flash.

Photo via CNET.