Now this is wild - a hybrid harddrive that mixes both NAND flash and a spinning disk!
The NAND drive is used as a buffer cache for write disk operations. First of all it is an extremely fast read cache (just compare the latencies for flash read with the regular latencies that come from disk seeking). This also means that a smart "elevator" algorithm is now built-in, as it will internally reorder disk writes to optimize buffer flush in a minimal number of rotations, and with minimal head repositionings. Not only that, but most of the time, the spinning disk motor will be now idle.
Interestingly enough, the new device was created by Samsung and Microsoft.
Samsung Electronics Co., Ltd., the world leader in advanced memory technology, today announced that its OneNAND Flash memory has been incorporated into the design of Microsoft Corp.'s prototype Hybrid Hard Drive (HHD), the first fully functional disk drive to combine NAND-based Flash with rotating storage media. The hybrid drive, designed to work with the next version of the Windows operating system, code-named "Longhorn," is being exhibited for the first time at the Windows Hardware Engineering Conference (WinHEC) in Seattle at the Washington State Convention Center from April 25 to April 27.