Although the current storage technology of choice for tablets is NAND flash memory, the Singapore-based A*Star Data Storage Institute (DSI) believes that in the future the need for high-capacity local data storage will drive thin hybrid drives into tablets. To enable such devices, DSI has developed an axial field motor that is very thin and efficient.
Currently, the thinnest hard disk drive in the market for a 2.5" form-factor is about 7mm thick. In order to break into the media tablet market, the ideal thickness of a hard disk drive should be 5mm or less. Researchers at DSI aim to produce a 2.5" hard disk drive thin enough to fit into a tablet, taking the thickness of the current iPad2 (which is at 0.34" or 8.8 mm) as the benchmark target.
One of the main challenges faced in scaling down the thickness of a hard disk drive is the ability to scale the thickness of the current spindle motor while maintaining the motor performance such as the non-repeatable run-out (NRRO). DSI has designed an axial field motor (the current motor is based on a radial field design) that is 4mm thick, and can spin at 5400/7200 revolutions per minute (rpm). The axial field design eliminates cogging torque and unbalanced magnetic pull that in turn helps to reduce friction loss of the bearing, vibration and acoustic noise. This slim spindle motor will be utilized in DSI’s thin drive with a 5mm thickness.
The DSI has also proposed a hybrid architecture in order to mitigate the issues of portability, reliability of data, and power consumption. Compared to flash or solid state drives (SSD), hybrid drives - which combine rotating media with NAND flash memory - can provide a larger storage capacity, and performances at a significantly lower cost; whilst compared to hard disk drives, hybrid drives can reduce power consumption by about 30%, according to DSI.
It is indisputable fact that hard disk drives and hybrid hard drives provide higher storage capacity than solid-state drives powered by NAND flash. The capacity will definitely be needed for tablets with Windows 8 operating system.
However, it remains to be seen whether specially-designed hard drives will actually be used inside mainstream media tablets. Since HDDs rely on rotating media, they are less reliable than flash-based storage in tablet usage conditions; for example, tablets are not used on firm surfaces like notebooks or desktops and are carried around all the time, which increases risks of damaging media surface with HDD's heads. Even despite of not really positive prospects within mainstream media tablets, DSI's 5mm HDDs may find a niche on the expanding tablet market that is projected to reach over 200 million units by 2014.
“DSI is very excited about the direction that we are taking. We strongly believe there is an opening in the market for thin drives. We are capitalising on our years of R&D experience in hard disk drive and data centre technologies and are working passionately to make the concept of thin hard disk drive into reality,” said Pantelis Alexopoulos, executive director of DSI.
At present, DSI's 2.5" HDD that is 5mm thick is a concept. No large HDD maker has adopted it or disclosed plans to make such drives. Furthermore, the severe flooding in Thailand and consequent halting of hard drives and components manufacturing facilities will likely slowdown adoption of new technologies. At the end of the day, Toshiba has 1.8"/5mm thick hard drives in its portfolio and those drives have been qualified by large PC makers already.