Seagate's first attempt at a hybrid hard drive was the Momentus PSD in 2007. The NAND controller and firmware were problematic, and costs were high. The NAND was used as a fast cache, with new adaptive algorithms powering the drive to near SSD performance levels. SSDs are used to cache frequently accessed data, while much cheaper hard drives store long-term data.
The second generation Momentus XT doubles the SLC cache to 8GB, while dual platters provide 750GB of storage. Seagate has sold over 1 million hybrid hard drives already, and has plans for a third generation Momentus XT using Multi-Level Cell (MLC) NAND flash. Seagate today announced the third generation of its hybrid drive, the Momentus XT. This time around, Seagate has doubled the NAND flash to 8GB and increased capacity to 750GB. Seagate also said the Momentus XT hybrid drive comes close to matching the performance of market-leading solid state drives (SSDs) that are more than twice as expensive.
Besides more memory and a faster drive interface, Seagate has added what it calls FAST Boot, which cuts a computer's boot time in half compared to the previous generation Momentus XT. During an initial OS installation, the Momentus XT captures boot files and places them in a special segment of the NAND flash where they remain for the life of the drive. The feature ensures that the drive always boots from flash and not spinning disk. The previous model Momentus XT was a combination of a two-platter, 7200rpm Serial ATA hard disk drive and 4GB of NAND flash and 32MB of DDR3 cache memory. Seagate did not provide read/write speeds on that drive. According to Joni Clark, Seagate's product marketing manager, the company has switched NAND flash vendors. Seagate also upgraded the drive interface from 3Gbps SATA to 6Gbps SATA.
Seagate said conducted performance tests against an Intel consumer-class 320 series SSD. Clark claimed the Intel SSD only beat the Seagate Momentus XT on boot times by 2 seconds. Ours costs [$245] for 750GB. Like the previous Momentus XT, the current model is a 4K sector drive, meaning it will not work well with Windows XT or earlier platforms; those OSes are tuned for 512Kbyte sector drives. Unlike the second-generation Momentus XT, when Seagate only had computer-maker Asus as an early evaluator of the drive, the company has seven equipment manufacturers qualifying the drive for use in their systems. Clark said Seagate has also "tweaked" its Adaptive Memory algorithm for better performance. Data is also copied first to the hard drive and then to the NAND; that ensures that if the NAND fails, data will not be lost. "If the NAND ever fails, you'll still have a perfectly good 7,200rpm hard drive," she said.
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