The hybrid drive gets a capacity boost and more NAND cache
In the storage world, nothing matches a solid-state drive for speed, and nothing matches a mechanical hard drive for capacity and price per gigabyte. Recognizing these two great tastes would go great together, many vendors have attempted to find the perfect hybrid storage solution, with variable—and often clunky—results. Seagate’s Momentus XT, which we first reviewed in September 2010, offered a 500GB 2.5-inch drive with 4GB of NAND flash with an adaptive algorithm to ensure that the most frequently used files are mirrored in the NAND. This means your boot drive feels faster than a mechanical drive, if only for the stuff you use the most. We liked the first Momentus, but complained that it could use more NAND. Seagate aims to remedy that complaint with this new Momentus.
The Momentus XT ups the mechanical portion of the drive to 750GB, while doubling the NAND cache to 8GB. The SATA controller is now 6Gb/s, the industry standard for all new drives. Unlike other hybrid solutions, the onboard controller performs the entire caching computation, so there’s no CPU hit. And there are no weird driver issues or frustrating installation procedures—we’re looking at you, OCZ RevoDrive Hybrid. Seagate’s adaptive memory algorithm simply moves the most-accessed LBAs to the NAND cache.
It might look like an ordinary 2.5-inch mechanical drive, but the Momentus XT is packing 8GB of NAND cache and three-quarters of a terabyte under the hood.
On the raw disk level, the Momentus XT 750GB is identical to a standard Momentus 750GB drive, as borne out by low-level benchmarks like HDTune. The adaptive algorithm shows its worth in real-world benchmarks and tests, such as PCMark Vantage’s HDD subtest and PCMark 7’s secondary storage suite. As we ran PCMark Vantage multiple times, the algorithm copied the LBAs we accessed most to the NAND, bringing the HDD subscore from a first run of 5,471 to a stable score of 14,759. That number is three times higher than what the standard Momentus is capable of, but it doesn’t come close to 52,000-plus score a second-gen SandForce drive can rack up. In the more modern PCMark 7, scores stabilized around 3,295—almost double that of the standard mechanical drive, but nowhere near the 5,070 of the SSD. When we installed Windows on the drive, our system stabilized at a boot time of around 25 seconds—just a few seconds slower than a SandForce-powered SSD, and a solid 13 seconds faster than the vanilla Momentus.
The ongoing hard drive shortage makes prices on existing drives, and thus the Momentus XT’s value proposition, difficult to determine. At press time, the 750GB Momentus XT’s MSRP of $245 makes for a $95 premium over the street price for existing stocks of the first-gen 500GB Momentus XT, or the vanilla 750GB Momentus, but those existing stocks could run out any time. A 120GB SSD would presumably cost about the same as the 750GB Momentus XT, but would deliver just a fraction of the latter drive’s capacity.
The 750GB Momentus XT offers a solid speed boost in real-world applications that you use frequently, compared to a regular mechanical drive. Its updated capacity, 6Gb/s SATA controller, and 8GB of NAND are much appreciated. If you don’t want to deal with clumsy multi-drive hybrid solutions or shell out for a tiny SSD, the Momentus XT offers an easier, better way to get both capacity and speed.
Significantly faster than a conventional mechanical HD; significantly more storage capacity than an SSD.
Not as fast as an SSD; less storage capacity than a conventional mechanical HD.
Momentus XT 750GB
Corsair Force GT 120GB
Avg Read (MB/s)
Random-Access Read (ms)
Avg Write (MB/s)
Random-Access Write (ms)
Premiere Pro (sec)
PCMark Vantage HDD
PCMark 7 Secondary Storage Suite
Windows 7 Boot Time (sec)
Asterisk (*) denotes best score. Our current test bed is a 3.1GHz Core i3-2100 processor on an Asus P8 P67 Pro (B3 chipset) running Windows 7 Professional 64-bit. All tests used onboard 6Gb/s SATA ports with the latest Intel RST drivers.