To test a current implementation and to determine how much improvement you can expect over the long term, we ran a special version of WorldBench 7 six times using a 750GB Seagate Momentus XT hybrid drive with its 8GB internal SSD.
Over the course of the six runs, system boot times dropped from 35 seconds to 31 seconds, and the WorldBench 7 score rose from 112 to 116. That's about a 12 percent improvement in boot times, and a 4 percent jump in WorldBench. However, the WorldBench 7 score of a nonhybrid, 5400-rpm drive also climbed by 4 percentmost likely due to Windows 7's own caching technologies. The standard drive showed no decrease in boot times, so the current Seagate hybrid drives do offer some benefit.
WorldBench 7 measures application performance, not the load times of the applications themselves, though subjectively the load times seemed only slightly faster after the first pass in my hands-on tests when I eliminated the Windows prefetch and swap file. Let's call that further, marginal evidence that a hybrid can make a positive difference in your everyday computing. Just for comparison's sake, a good SSD scored more than 40 points higher on WorldBench 7 on the same system.
The specs for the upcoming Toshiba and Western Digital hybrid drives weren't available at the time of this writing; however, you might see models with 16GB or even 32GB SSD portions that provide a greater increase in performance. The larger the SSD in the hybrid drive, the more data you can cache and the less often you'll need to load data from the hybrids slower mechanical drive. Integration and interaction with operating systems could also boost hybrid performance, assuming of course that a significant drop in SSD prices doesn't render the technology moot.
As of October 10, 2012, a standard 750GB, 2.5-inch hard drive was about $80, a 750GB Momentus XT SSHD was about $130, and a brand-name 128GB SSD also cost about $130. Given those prices, current hybrid drives really make sense only in laptops, and only when you want high performance and more storage capacity than an SSD can provide.
In a desktop PC with unoccupied drive bays, you'll get much better bang for your buck with a stand-alone SSD combined with one or more mechanical hard drives. Even for a laptop, a smaller, more affordable SSD supplemented by an external conventional hard drive might better deliver the performance and the capacity you're looking for.
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