At the CES 2013, Western Digital has shown the hybrid drives units, with a thickness of only 5mm, with a demonstration of performance that places their units very close to a SSD in terms of performance.
Indeed, Western Digital has shown several units of 2.5″ form factor at their Blue and Black series, the latter combine traditional storage (magnetic), with a solid storage using Flash memory chips to form a hybrid drive or SSHD (Solid State Hard Drives).
Western Digital showed two 2.5″ units of its Black line, a 500GB and a 1TB capacity, combined with 24GB MLC Flash memory, although some units will come with 32GB, 24GB or 16GB of MLC flash memory, which depends on the requirements of the OEM. Of course, while the 500GB drive has a thickness of 5mm, the 1TB drive is 7mm thick because it adds another magnetic plate, yet perfectly thin enough to Ultrabooks devices as compared to the 1TB 2.5″ traditional having a thickness of 9.5mm.
Western Digital did a little demonstration of performance load consisted of a suite of applications, where a traditional disk took 81 seconds, while an SSD did in 51 seconds, while the hybrid drive from Western Digital was delayed 55 seconds, very close to the SSD.