Western Digital Still Evaluating Hybrid Hard Drives
A few years ago, back when SSDs were much smaller and far more expensive than they are today, hard drive manufacturers began talking up what they called a hybrid hard drive, or HHD. Like the best combination of chocolate and peanut butter, HHD's were billed as potentially delivering significantly more performance than any conventional drive while remaining far below the premium price point of pure solid-state drives.
Seagate's Momentus Hybrid Hard Drive
While theoretically the perfect answer to the price/performance gap between HDDs and SSDs, Hybrid hard drives have never materialized in quantity. Seagate is the only company that's recently launched a drive; we reviewed its Momentus XT last summer. Western Digital has an consumer-oriented SSD product line dubbed Silicon Edge Blue, but a visit to the company's website illustrates that SSDs are a small segment of WD's larger business plan.
Western Digital's studied nonchalance may be a smart move in the long run. At present, flash memory faces serious scaling problems below 25nm. While there are multiple companies working to resolve the data retention / lifespan issues, many of the potential changes will themselves impact either manufacturing cost or drive performance. These problems won't prevent SSDs from continuing to gain market share, but they aren't going to overturn and replace conventional hard drives.
The other factor Coyne cited as a strike against SSDs/HHDs is the current state of OS support. "We look out into the future where such a device would be supported by operating system capability, which it is not really supported well today," Coyne said. "As we look at that over the next couple of years, we see an emerging opportunity for such a device family to offer performance capacity and value."
This is a solid point. In theory, the flash memory built into a hybrid drive acts as a further buffer zone between the CPU and the need to access the achingly slow physical hard drive. Simply plugging flash into the system, however, doesn't exactly do the trick. In order to take full advantage of the cache, Windows needs to know what sort of data it should keep there. Equally important is the need to limit the number of read/write cycles to the flash cache itself—constantly updating small portions of the cache could lead to abnormal wear leveling or shorten the flash memory's lifespan.
We wouldn't be surprised if WD's next-generation VelociRaptor hard drive, when it eventually appears, is an HHD. Until better algorithms and OS support are both in place, however, it may make good sense for the established HDD manufacturers to primarily focus on their traditional mobile/desktop/enterprise products. Further advances in solid state technology may eventually combine the price of spinning media and the performance of SSDs, but it's not going to happen anytime soon.