Japanese researchers claim to have produced the most densely packed hard drive in existence.

The team at Tohoku University's Research Institute of Electrical Communications has produced a prototype drive with an areal density of 138GB per square inch. As such, their one-inch drive - frequently used in devices such as digital music players - packs in a hefty 10GB.

Head of the project, Yoshihisa Nakamura, explained the prototype drive uses perpendicular recording to achieve the higher density. It works by standing the magnetic fields that represent data bits upright. In commercially available drives, those fields lay flat on the surface of the disk. Standing these fields upright means they take up less space, enabling more data to be crammed on the disk.

"For one-inch drives, 138GB areal density is a world record. Somebody may have a higher density in a lab somewhere, but they haven't shown them," Nakamura said.

Nakamura said his lab should be able to boost the areal density further to about 500GB per square inch in 2007 - paving the way for 30GB one-inch drives. Currently, the highest-capacity one-inch drives store a maximum of 6GB.

Many of the world's leading drive vendors have announced they plan to sell drives using perpendicular technology. Of these companies, Japan's Hitachi Global Storage Technologies (HGST), Fujitsu and Toshiba have worked with Nakamura to develop the prototype, he said. HGST is considering commercializing the drive, although the company has not said when.

Tohoku University researchers aren't the only ones looking to perpendicular recording as a way to boost areal density. Last month, Japanese public broadcaster Nippon Hoso Kyokai (NHK) showed a prototype 10GB one-inch hard drive that also employed the technology.

That drive, which was developed by NHK and Sony, has an areal density of 120GB per square inch, according to Eiichi Miyashita, senior research engineer at NHK's Science and Technical Research Laboratories. There are no plans to commercialize this drive yet, he said.