The hybrid hard disk drive market is expected to reach 600 million units in 2016, according to market researcher Objective Analysis. This would mean an explosion of mainstream drives that integrate the performance-boosting benefits of flash memory.

Seagate&39's Momentus XT Solid State Hybrid Drive can add a lot of performance on certain tasks with just a touch of flash memory.

The first generation of hybrid drive technology was "well conceived but poorly implemented," according to a report released on Monday by Objective Analysis. "Now that working versions have been implemented the hybrid drive promises to sweep the PC hard drive market."

"We expect the hybrid drive market to nearly double every year for the five years following its initial adoption, reaching 600 million units by 2016," said analyst Jim Handy, who authored the report, in a statement. "This blazing growth will result from hybrid drives replacing standard HDDs in mainstream PCs."

Hybrid drives, in their current form, add a small amount of flash memory to a traditional spinning HDD. But this pinch of flash can deliver a big boost to performance on certain tasks at relatively little extra cost, as CNET Reviews demonstrated with the 500GB Seagate Momentus XT and as other reviews of the Seagate drive have shown.

"The NAND [flash memory] in these hybrid drives will be pretty small. Seagate's Momentus XT does a really good job with only 4GB of flash, and Nvelo's Dataplex software accelerates HDDs very well with only 16GB of NAND," said Handy, responding to an e-mail query.

Handy continued. "We expect the hybrid drives released in 2010 and 2011 to be introduced around the 4GB level, but over the forecast period, the amount of flash per drive should ramp to an average of 16GB."

The upside for consumers is that they're not as expensive as flash-only solid-state drives, which can add hundreds of dollars to the price of a traditional HDD. "A 4GB NAND--using SLC [single-level cell] NAND flash, which is required in this application--should add about $20 to the manufacturing cost of an HDD today, which might translate to an added $30 to 40 to the end user."

He continued. "A lot of consumers would be perfectly happy to spend an extra $30 to 40 to get the performance of an SSD and the capacity of an HDD. So far they have not been happy to spend an extra $200 to 500 to get an SSD that's smaller than an HDD."

In the case of Apple's just-announced MacBook Air, for example, adding just 128GB of flash storage to the base configuration increases the price of the 13-inch model from $1,299 to $1,599. And choosing a 256GB solid-state drive over a 500GB hard disk on a 15-inch MacBook Pro adds a whopping $650 to the price.