Seagate has launched the Momentus 5400 PSD laptop-use hybrid hard drives, featuring 256MB of embedded Flash memory for faster boot-up and better system performance. "What you do is take a logical address of a hard disk drive - say, sector 0," Barnetson illustrated for us, "and rather than having it reside on magnetic media, you say it now resides on Flash media. Any operations that are done to it, whether they be read or write, are not so much cached as they are pinned, or physically moved from the magnetic media over to the Flash memory." A sector which contains frequently accessed files or other elements, such as a FAT table, could be pinned to Flash memory for faster read and write performance, he said.

Once a logical address is pinned to Flash, I/O requests to that address are automatically redirected to the cache. This is somewhat different from the dynamics of a memory cache, where elements of memory in the vicinity of the address currently being accessed are copied into the cache, since those other addresses in the neighborhood are the ones most likely to be addressed next. Once a memory address falls off the "page" in the memory cache, it's refreshed with the addresses in the same page of the next address. This is not at all how a hybrid HDD cache works, Barnetson was clear in illustrating. "Once you pin a sector, you just read and write to it as you normally would; it's just that the drives will respond more quickly," he stated.

According to InformationWeek, the 5400 PSD 2.5-inch hybrid HDD has 160GB of storage capacity and sells for $190, “which is almost a 30% premium over a traditional drive of equal storage”. This Seagate’s Power Savings Drive for notebooks can quicken the time it takes to boot a PC by 20 percent, and uses half as much power as a traditional hard drive reportedly.

Because of the flash memory, you get a high reading and writing speed. The drives decreases battery/electricity consumption, and heat and prevents data loss due to vibrations. The first notebook with the Seagate Momentus 5,400 PSD will be the Sony Vaio SZ650, which gets 25% more battery life from using the hybrid drive. The higher plattery density will negate some or all of the speed advantage. There are more factors that just the speed of the drive that will determine how it long it takes to get data.

On the other side, ExtremeTech reports hybrid drive technology is not delivering the “order of magnitude” improvement it originally promised, due to first-generation, non-tuned drivers for the Vista operating system. Hybrid drives really have a long way to go and maybe once its 4gb+ of ram we'll start to see a difference, but my feeling is by that time magnetic drives will be a thing of the past as ssd's are getting cheaper all the time. The Momentus 5400 PSD’s specifications say it will be additionally available with 80GB and 120GB capacities. The drive has 5400rpm rotational speed and uses a 1.5Gb/s SATA interface.