A thinner hybrid hard disk drive (HDD) intended to serve as storage media for new computers like Ultrabooks and less bulky than a rival storage form could help the HDD industry in its unremitting battle against tablet devices, according to an IHS iSuppli Storage Space market brief from information and analytics provider IHS. While the current form of storage for the super-thin Ultrabook laptops produced this year is the hard disk drive containing a cache solid state drive (SSD) element, that form factor at 7 millimeters is still considered too thick and too slow when compared to tablets like the iPad from Apple Inc. Since their appearance on the market two years ago, tablets—with their slim profile and fast "instant-on" capabilities—have eaten mightily into the sales of notebook PCs, whose performance and ease of use have suffered in comparison. A new and thinner hybrid HDD measuring just 5 millimeters aims to change all that. Unlike the rival hard disk drive with cache SSD form of storage that combine two different physical drives into one unit along with software, hybrid HDDs are basically hard disk drives containing a built-in layer of NAND flash memory. Not only do hybrid HDDs offer a new way to store data, their thinner profile also would be ideal for even slimmer and lighter, next-generation Ultrabooks, the computing device that PC players are hoping would provide the best chance to win the war against tablets. A thinner hybrid HDD—especially one measuring 5 mm that is obviously more compact than current 7-mm drives—also has other advantages. It can be swapped with older hard disk drives, is less expensive than pure solid state drives, and can serve in a larger market than just Ultrabooks and SSD-based notebook PCs. For instance, thin hybrid HDDs can also be used in market segments such as the external hard disk drive sector, all-in-one desktop PCs, gaming platforms, and even tablet PC designs. Shipments of hybrid HDDs are expected to surge by a factor of six in the course of four years, rising from 1.2 million units this year to 25.0 million units by 2016. In comparison, the rival hard disk drive with cache SSD will see shipments rise at a slightly less expansive rate, climbing from 9.8 million units in 2012 to 64.2 million in 2016. Depending on the resulting performance of the hybrid HDD products now in development as well as their eventual price point, the 5-mm hybrid HDD could potentially replace many conventional hard disk drives, including the 9.5-mm and 7-mm HDDs currently used in notebook PCs. All told, the potential market for 5-mm hybrid HDDs could amount to more than 100 million units by 2016, which includes the market for notebooks that do not currently use pure SSDs, hard disk drives with cache SSD, or any form of hybrid HDD. As such, the 5-mm hybrid HDD could considerably revive the ailing notebook market and help it become competitive again. Both the storage industry and the PC market would benefit in the process. Manufacturers focus development efforts on the hybrid HDD Hybrid HDDs have been on the market since Seagate Technology and Samsung Electronics introduced their versions in 2006 and 2007, respectively. However, their benefits to users were not particularly evident, given that the hybrid HDDs at that time had lower storage capacity of less than 160 gigabytes, slower speed of 5,400 revolutions per minute, and limited flash memory of 256 megabytes. Seagate upped the ante earlier this year by developing its third-generation hybrid HDD, the Momentus XT—boosting HDD capacity to 750 gigabytes and cache to 32 megabytes, as well as increasing speed to 7,200 rpm. Even so, the 8-gigabyte flash memory was still too low for the Ultrabook minimum requirement of 24 gigabytes. The Momentus XT also did not meet the 7-mm thickness requirement for Ultrabooks, whose specifications for the notebook initiative were set by Intel Corp. Then in May, HDD manufacturers and Seagate rivals Western Digital and Toshiba announced separately that hybrid HDDs were in development at both companies. Toshiba, working with internal sources to secure NAND flash, is now expected to launch a 7-mm hybrid HDD this year and a 5-mm hybrid HDD product by next year. For its part, Western Digital—believed to be working with SanDisk to obtain NAND flash for its own version of a thin hybrid HDD—is anticipated to expedite development of its new product as a result of knowledge it has picked up from other companies. With new Ultrabooks next year expected to adopt the 5-mm hybrid HDD as soon as the new storage media become available, more notebook PC manufacturers will initiate their own adoption of thin hybrid HDDs, IHS iSuppli believes. Consumers will also reap significant improvements on their end, including a more efficient PC form factor, lower power consumption and greater cost-performance value.