The Seagate Momentus XT will initially be available in three capacities—250GB, 320GB, and 500GB. The drive you see pictured below if the flagship 500GB model.
The Seagate Momentus XT features 4GB of integrated SLC NAND flash, linked to the traditional platter-based storage via an intelligent controller. The drives conform to the 2.5” form factor with 9.5mm Z-Height, and they sport standard SATA 3.0Gb/s interfaces. 32MB of DRAM cache is also incorporated into the drives, and as we’ve already mentioned, they feature 7200RPM spindle speeds. Looking at the pictures above, there’s nothing that hints to the hybrid nature of the Momentus XT. They simply look like standard 2.5” hard drives. But, rest assured, they are different.
Although Seagate hasn’t revealed all of the secret-sauce that makes the Momentus XT unique in the current market, understanding how the drive works is fairly straightforward. The 4GB of SLC NAND flash is used as a high-speed repository of sorts. The controller on the Momentus XT monitors usage patterns and copies the most frequently accessed bits of data from the hard drive to the solid state storage. And it all happens independent of the OS or drivers. According to Seagate, the data on the hard drives has to be accessed multiple times before it is copied to the solid state storage and the contents of the flash memory will dynamically and constantly change over time, based on usage. To put it simply, the most commonly accessed data on the platters get's copied to the much higher performing, SLC Flash memory, which results in a performance boost.
Knowing how the adaptive memory on the Momentus XT works, reveals one of the drawbacks of a hybrid design such as this one—the flash memory will offer no performance benefit to infrequently accessed or new data. So, with large file copies, application installations, and the like, the Momentus XT will perform like a standard HD.