A storage odyssey 2010

DQW Bureau
07 Dec 2005


Crystal ball gazing has been a favorite pastime for the

scientific community for ages; it has also proved to be most beneficial in

heralding technological advances. Not only technical papers even sci-fi

fantasies by luminaries like Jules Verne, HG Wells or more recently Arthur C

Clarke have often turned into scientific realities. Dataquest looks at three

futuristic data storage technologies that might re-define the entire storage

paradigm in the years to come.

Blue laser technology

Conventional optical technologies such as CD, DVD and

magneto-optical (MO) drives write data using red lasers. But makers of storage

systems and recording media are developing ways to read and write using the more

efficient blue lasers. Because these lasers operate at shorter optical

wavelengths, they can write more data in the same space and write and read data

faster than devices that use red lasers.

Data storage on various optical media

Blue laser beams have a much smaller spot size than red

laser. A smaller spot size leads to smaller pits. Because of this, data on blue

laser optical storage disks can be stored more densely, up to five times as much

data than red laser technology. Current single sided DVD disks hold about 4.7 GB

data. DVDs using blue laser technology will be able to hold about 27 GB.

Two industry groups are promoting separate formats based on

blue laser technology, viz., Blu-ray Disc Founders comprising Sony along with HP

and Dell, and the DVD Forum represented by Toshiba and NEC. A traditional DVD

and a Blu-ray disk. The HD-DVD standard can hold about four times as much data

as today's DVDs.

Holographic storage

Holography breaks through the density limits of conventional

storage by going beyond recording only on the surface, to recording through the

full depth of the medium. Unlike other technologies that record one data bit at

a time, holography allows a million bits of data to be written and read in

parallel with a single flash of light. This enables transfer rates significantly

higher than current optical storage devices.


Both magnetic and conventional optical data storage

technologies, where individual bits are stored as distinct magnetic or optical

changes on the surface of a recording medium, are approaching physical limits

beyond which individual bits may be too small or too difficult to store.

Holographic data storage is a volumetric approach which, although conceived

decades ago, has made recent progress toward practicality with the appearance of

lower-cost enabling technologies, significant results from longstanding research

efforts, particularly led by IBM at its Almaden Research Center, and progress in

holographic recording materials.

To write onto a holographic disk, a laser beam is shot into a

prism so that it splits into two beams. One beam, called the object beam, passes

through a spatial light modulator (SLM) where it is encoded with the data from a

one-million bit page. It then goes on to meet up with the other half of the

split beam, known as the reference beam.

Magneto resistive technology

Magneto-resistive technology derives its name from a class of

materials that change resistance in the presence of a magnetic field.

Magneto-resistive recording heads utilize an inductive write head based on the

same inductive principles of earlier technologies combined with a

magneto-resistive element to provide the read function. These magneto-resistive

elements are designed and fabricated to provide many times the signal

sensitivity or reading efficiency of the inductive read head technology.

Magneto-resistive or MR head technology, again with research

pioneered by IBM, uses two elements: a thin film inductive write element, and a

magneto-resistive read element that changes its resistance to the flow of

electricity as the surrounding magnetic field changes. There are three primary

advantages of MR head technology over inductive head technology:

  • The read and write functions of an MR head are physically

    independent and separate. The physical separation of the two functions of the

    head (reading and writing) provide the capability of optimizing each design for

    reading and writing. Physically, the read head can be placed inside the write

    head. This translates into an overall smaller head dimension, allowing for

    faster head speed across the disk platter.

  • The MR head signal level is independent of the velocity of

    the disk, thus allowing for much higher RPMs, which will allow for closer spaced

    magnetic transitions on the disk, which, in turn, translates into increased

    storage capacity of the disk.

  • The MR read head and the inductive write head combination have a higher

    frequency response than a comparable density inductive head. This enables MR

    heads to read and transfer data at an ever-increasing pace, and maintain

    adequate signal-to-noise ratios in the face of constantly increasing areal