Hitachi Global Storage Technologies is set to quadruple the storage capacity of desktop hard drives within the next two years.

The company said that its new reading-head technology would allow users to cram more data on hard drives, enabling desktop and laptop drives to store 4TB and 1TB of data, respectively.

Hard drives are currently doubling in capacity every two years, said John Best, chief technologist at Hitachi Global Storage Technologies. The new reading-head technology will allow an even greater capacity boost while shrinking the size of disk drives, Best said.

The company hopes to implement the technology in hard drives in 2009.

As hard drives shrink, magnetic fields become harder to detect, so the reading head has to be more sensitive, Best said. The heads made with Hitachi's new CPP-GMR (current perpendicular-to-the-plane GMR) material are more sensitive than existing reading heads and detect the magnetic field better, Best said.

The CPP-GMR heads will enable the density of disk storage surfaces to increase to 500Gbit/s per square inch or more in the near future, Best said. The greater the density of the storage surface, the more data the surface can hold. The current density stands at about 200Gbit/s per square inch, he said.

The technology will help to meet future storage needs fueled by video and Web 2.0 applications, Best said.

The technology builds on GMR (giant magnetoresistance), a physical effect that manipulates the charge and spin of electrons, allowing an increase in density and storage on hard drives. The GMR effect won two European scientists, Albert Fert and Peter Grunberg, a a Nobel prize in physics this month.

GMR was discovered in 1988 and commercialised by vendors such as IBM, which used the technology to increase the capacity of its drives every year. The technology fueled the growth of information storage and led to miniaturised hard drives that could fit in portable storage devices such as the iPod.

Scientists consider solid-state, atomic-scale storage to be the future of data storage, but the emergence of solid-state drives (SSDs) won't make hard drives irrelevant, Best said. SSD is semiconductor technology and can't compete with hard drives on a cost-per-bit basis, he said.