How did Seagate squeeze so much capacity into a 2.5" drive? The answer is perpendicular recording, a new technology that delivers larger densities per square inch by storing bits perpendicularly to the disk plate. The older approach, which is still largely used in many popular drives, stores bits horizontally on the disk plate.

According to Seagate, perpendicular technology can reach recording densities of 500 Gbpsi (gigabit per square inch) which should eventually make it possible to stash up to 2TB on a single 3.5" drive. The new 2.5" drives have a capacity of "only" 160GB, but pushing perpendicular recording to its limits will open them up to storing a half-terabyte of data on a single device.

The drive market has been growing quickly for Seagate. "We shipped almost 70 million 2.5-inch drives in 2005, a remarkable increase over the 50 million shipped the previous year," says Joni Clark, product marketing manager at Seagate.

"We also noticed that customers were looking for larger and larger drives, which is why we saw an opportunity to develop perpendicular recording on those models," Clark adds.

If figuring out Seagate's laptop drive plans required some deductive reasoning, by contrast Western Digital's pre-CES announcement was just plain simple to understand.