According to Toshiba, one of the remaining three HDD manufacturers, about 50% of the mobile HDDs will be hybrid in two years. These hybrid HDDs combine traditional magnetic HDD storage with flash memory that serves as cache for the most frequently used files.
HDDs, including hybrid ones, won't come close to the performance of SSDs, but their advantage is that they can provide about four to eight times more storage as similar priced SSDs. Toshiba currently has 1 TB and 750 GB hybrid HDDs in its product line up. Both are 5400 RPM discs combined with 8 GB SLC NAND memory. A special algorithm monitors which data is used most often and caches this in the NAND memory, according to Toshiba these discs are about three times as fast as regular HDDs without flash memory.
Seagate and Samsung already introduced hybrid HDDs in 2006 and 2007 but they never got really popular. They are a cheap option in Ultrabooks as Intel requires flash memory in them. Apple also has similar technology which can be fitted in iMacs which goes by the name Fusion Drive.
Toshiba expects that in about 2 years about half of the 2.5" disks for mobile devices will be hybrid. But since laptops are getting thinner and therefor other form-factors like mSATA are gaining more popularity one might question if there will still be a lot of 2.5" disks sold in 2 years. As hybrid disks are pretty expensive, manufacturers might also opt for using small SSDs as cache memory by utilizing Intel's Smart Response technology.
