Reference:http://www.sciencedaily.com/releases/2013/05/130513114955.htm
Despite the increasing competition from alternative technologies such as solid-state drives,
magnetic disks remain an important data-storage technology. They are not only reliable
and inexpensive, but their storage density has potential for even further improvement.
One method under current investigation is storing each data bit in a single magnetic grain
of the thin film of the recording medium, rather than in several grains as in conventional hard
drives. Storage in single grains only would increase stability and reduce the magnetic fields
required to write bits.
The rise of the internet and the move from paper to digital information has driven a need for
large-volume electronic data storage. Maria Yu Lin and her co‐workers at the A*STAR Data
Storage Institute, Singapore, have now established some important design principles to consider
when developing bit patterned media recording (BPMR) -- a potential high-density magnetic recording
system of the future.
Conventional hard disk drives store a single data bit in a continuous magnetic medium consisting of
many 'grains'. However, the number (approximately 10-15) and the size of these grains (about 6-10
nanometers) naturally limits the maximum density at which digital information can be stored. The
BPMR technique will offer much higher storage capacity because it is suppose to records the data in a regular array of
single-grain magnetic islands (see image) that can be much smaller than multiple grain bits in
continuous media.
There are several problems of the useing of BPMR in computer hard disks.
One problem is that the islands are separated by non-magnetic spaces of the
surface only is magnetic. The data can be passed from the writing `head' only when it is aligned
with an island on the spinning disk. Therefore the writing process must be synchronized with the
position of the magnetic islands. However, manufacturing defects, variations in disk spinning speed
and vibrations can all cause temporal misalignment, which in turn causes writing errors.
Adding information to the disk that tells the writing head its exact position is one way to correctly time
the writing process. This includes synchronization sectors and error correction information; however,
this information reduces the capacity of the disk for data storage. After theoretical analysis it could be deduced that
compare to the potential gain in terms of data density this technology enables, such a total overhead is acceptable."
