We reported yesterday that Seagate is discontinuing its 2.5-inch 7200 RPM consumer hard disk drives, leaving an apparent hole in its consumer drive lineup between value-oriented 5400rpm HDDs and its faster Momentus XT hybrid disks (which incorporate NAND flash as a disk cache). The reasoning for that discontinuation has become clear this morning, as Seagate is expanding its hybrid drive offerings to fill as many of the holes as it possibly can.

Gone is the "Momentus XT" brand, which used to denote Seagate's hybrid hard drive + NAND disks—the new name for the entire hybrid line is "Solid State Hybrid Drives," or SSHDs.

The rebranding change affects not just the 2.5-inch mobile form factor, but the 3.5-inch Momentus XT desktop drives as well—it's all SSHDs starting this quarter. Anandtech has the most easily understandable chart for the new lineup, but the summary is that the 2.5-inch SSHDs come in 500GB and 1TB flavors and cost $79 and $99, respectively; the 3.5-inch SSHDs are available in 1TB and 2TB sizes and cost $99 and $149. All include 8GB of MLC NAND, which acts as a read and (apparently limited) write cache.

The pricing is a bit of a premium over non-SSHD disks, but Seagate claims that the performance benefits more than offset the cost. The 2.5-inch SSHD devices all spin their platters at 5400 RPM, but the 8GB of NAND should enable the disk to perform far better than a regular HDD on cache-friendly workloads (which generally include standard browsing and office-type work). One of the key measures of subjective computer speed is "snappiness," or how quickly the computer responds to user input; the key to the SSHD's success will be the accuracy and effectiveness of its caching algorithms and how smart the drive is about holding needed data in cache. A smart controller will mean better caching, which will mean less user input lag when opening applications or documents, which will mean a happier user.

Seagate's new drives are shipping as of today.