Microsoft has outlined a new hybrid hard drive that will work to make Windows Vista more efficient.

The new drive for laptops, called ReadyDrive, could run faster and last longer on a single battery charge by including NAND flash memory as a disk cache.

It would also reduce the number of hard disk crashes due to shocks - "The most common hardware failure in notebooks," according to Microsoft, by decreasing the amount of time the disk needs to be spinning.

Laptops will be the first to use the technology, but its potential is much broader, said Ruston Panabaker, an architect in Microsoft's Windows hardware innovation group. "We fully expect to see it show up in desktops and perhaps even in specific server applications," he said.

ReadyDrive has spawned a new category of flash-assisted hard drives. Both Samsung and Seagate have announced hybrid drives that integrate a 1.5-inch magnetic hard disk with up to 256MB of Flash memory.

Both are expected to be available early next year. A competing technology from Intel, codenamed Robson, places the cache on the motherboard, along with a controller chip. Robson will launch with Intel's Santa Rosa notebook platforms in the first quarter of 2007.

"The interface to flash chips has been doubling in read and write performance every single year," Panabaker said.

This year market research company IDC predicted that flash prices would drop by 55 percent. Halfway through 2006, prices have already exceeded projections. Current prices have dropped into the $17.50 per GB range, and the trend is expected to continue.

Because disk I/O speeds haven't kept up with CPU horsepower gains, it was just a matter of time before storage vendors turned to flash.

"Vista was certainly the catalyst," said IDC analyst John Rydning, but the use of hybrid drives could well expand beyond Windows systems.

A related Vista feature, ReadyBoost, is a read cache that allows Windows to cache memory pages that won't fit into main memory on a USB flash drive. Because the Flash device could be removed at anytime, however, unique data cannot be stored on it and data is encrypted for security reasons.

ReadyDrive can also cache portions of the operating system for faster boot up and resume times.

"I would expect to see a 30 percent boot time savings," said Panabaker. During normal operations, data retrieved from the cache will be transferred two to three times as fast as from disk, Panabaker said.

Samsung claims that the cache in its hybrid drive is 50 times faster than disk.

Not all applications will benefit equally from hybrid disks, however. The biggest performance improvement comes from faster seek times - the time it takes to locate data on disk.