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The Seagate Momentus XT is a rather unusual 2.5in SATA laptop hard disk. As well as having a 7,200rpm spindle speed and a SATA II connection, it also has 4GB of SLC flash memory. Seagate claims that this boosts performance to near-SSD levels but at a dramatically lower cost and with much more storage space.
We were rather sceptical of these claims since the last attempt at pairing flash memory with a hard disk, Intel’s Robson technology from a couple of years ago, was a failure. The XT was impressively quick in our file transfer tests though, where it was far faster than a 5,400rpm laptop disk and comparable in performance to a 7,200rpm desktop disk. Large files were written at 80.3MB/s and read at just under 92MB/s. Small files were written at 38.6MB/s and read at 28.1MB/s.
However, standard 7,200rpm hard disks are just as fast at copying small files and only 20MB/s slower at copying large files. Neither can come close to the fastest SSDs which have other benefits too, such as potentially increased battery life and greater durability due to their lack of moving parts.
The XT’s speed gains only occur when the disk deals with the same type of file repeatedly, such as in our file transfer tests which copies the same batch of files to and from the disk 100 times. This repeated usage allows the disk’s Adaptive Memory technology to cache the files being worked on to the flash memory, speeding up access times. On tasks with a more unpredictable set of files, such as loading a level in the game Crysis, the Adaptive Memory technology doesn’t kick in. In this Crysis test, the XT loaded the entire level in an unremarkable 39 seconds.
The file copying performance of the Momentus XT is impressive, but this speed gain only occurs in certain circumstances and it’s also expensive compared to standard laptops disks at 21p per gigabyte. Even if you want fast storage in a laptop, but can’t afford an SSD, these issues limit the XT’s usefulness and appeal greatly, so think carefully about how you use your computer before buying.
