Seagate Technology LLC has started shipping a notebook PC hard drive that overcomes an obstacle many feared would be a major roadblock to the further expansion of disk capacity — and the overall growth of the storage industry.

The new approach that aligns bits of data vertically rather than horizontally enables Seagate — and other drive vendors — to further boost the density of drives without increasing the risk of scrambling data.

Since the first hard drive was introduced 1956, bits have been arranged in a flat, horizontal fashion on the spinning platters. To boost capacity, engineers reduced the size of the particles whose magnetic state is what actually remembers data.

But with some drives now topping out at 500 gigabytes, the miniaturization is nearly at its limit. Made any smaller, the particles can begin to interfere with the magnetism of their neighbors. The result is disastrous for data.

By storing bits in a vertical, or perpendicular, arrangement, engineers are able to boost capacity by taking advantage of the real estate that is freed up.

It's a major change that all drive makers are in the process of undertaking, said John Donovan, vice president at the research firm TrendFocus.

"It a whole new way of doing things," he said. "Not only do you have to change the thinking, but the tooling, the way the heads and disks interact with each other."

Seagate's new drive, the Momentus 5400.3, was being shipped as of Monday, the Scotts Valley, Calif.-based company said. The shift to perpendicular recording allows it to bump up the maximum capacity of its notebook drive to 160 gigabytes from 120 gigabytes.

The 2.5-inch drive costs $325, compared to about $240 for the 120 gig model. Seagate plans to extend the new recording technology to other notebook drives, as well its 1-inch drives used in handheld gadgets and 3.5-inch drives for desktop PCs.

"Our transition to perpendicular technology increases our ability to meet the needs of our growing customer base," said Karl Chicca, general manager of Seagate's Personal Storage unit.

Other drive makers also have either announced products or plans that include perpendicular recording. At the Consumer Electronics Show earlier this month, Toshiba unveiled its second 1.8-inch drive that relies on the new technology.

Perpendicular recording has benefits beyond boosting storage density by reducing the need for additional components, said Mike Hall, a Seagate spokesman.

"If you can reduce the component count, you reduce the power drawn, you reduce the heat and you reduce the wear and tear," he said.

In the next three to five years, the new technology is expected to increase maximum drive capacities five fold, Hall said.