Hitachi Global Storage Technologies (HGST) will later this year begin selling hard-disk drives based on perpendicular recording, a yet-to-be commercialized recording method that should enable engineers to continue increasing drive storage capacity beyond today's limits, HGST is due to announce today.

The company is already testing sample drives based on perpendicular recording and says the technology could allow for 1TB desktop drives or 20GB Microdrives in 2007.

Perpendicular recording is perhaps the most significant near-term step in the evolution of hard-disk drive technology. The method is similar to the longitudinal recording used in today's drives in that it relies on magnetically charged particles for data storage. In today's drives, the north and south poles of the magnetic particles run parallel to the disc but in the new method they are arranged perpendicular to the disc, as the name suggests.

The result of this new arrangement is that each particle occupies a smaller area of the disk's surface and so more particles can be crammed onto the disk. This is measured as the areal density and today's most advanced drives can store between 100G bits and 120G bits of data in a square inch of disk space.

"Without [perpendicular recording], existing technology will stall at about 120- or 130G bits per square inch," said John Best, chief technologist at HGST. "Longitudinal recording is running into significant problems with bit size."

In contrast, HGST sees drives based on the new method with areal densities of around 230G bits per square inch in 2007, Best said. Such a density would enable the 1T-byte, 3.5-inch drive and 20G-byte, 1-inch drive, he said.

HGST's first drives are likely to offer a more conservative storage density of about 120G bits per square inch and be available later this year. The company is currently field testing a 100G-byte, 2.5-inch drive based on an 80G bits per square inch version of the technology, said Best.

Good news for users is that the new drives shouldn't be substantially different from current drives in terms of mechanical performance or price.