WD Introduces Hybrid HDD

Western Digital's new hybrid HDD is only 5mm thickWestern Digital Corporation on Monday announced that it is sampling its long-awaited hybrid HDD.  WD claims that the 500GB 2.5″ device is the thinnest in the industry at 5mm. So far Seagate has been alone in this field with its Momentus XT Solid State Hybrid Drive.  There are some significant differences between the two drives:

  • Seagate uses SLC flash while WD uses MLC.  There is more than a 10:1 price premium for SLC flash
  • Seagate’s hybrid ships in 750GB and 500GB capacities while WD’s is 500GB
  • Seagate’s device is 9.5mm thick, while WD’s is 5mm

The last point is extremely important.  Intel is really promoting the new Ultrabook form factor, and it is difficult to put a drive that is larger than 7mm into the Ultrabook’s thin profile.  Furthermore, Ultrabook performance specifications require a modicum of solid state storage which most OEMs are providing as a separate SSD in addition to a standard HDD.  A hybrid drive would allow these OEMs to omit the SSD altogether. The SSD Guy was able to hold one of the WD hybrids at the Intel Developer Forum today – it’s impressively small!

Rumors indicate that the WD hybrid has a 16GB cache compared to Seagate’s 8GB cache, but WD hasn’t yet formally announced its cache size.  Since some SSD makers argue that a 16GB MLC SSD meets Ultrabook performance specifications under Intel’s SRT caching software, a 16GB cache would seem to be a reasonable size for a hybrid drive. Objective Analysis is bullish on hybrid HDDs: HDD makers already put DRAM caches into their drives.  Why shouldn’t they convert this cache to a DRAM-plus-NAND rendition?  We have published a report that examines this market in depth and forecasts its impact on the SSD market.  This report: Are Hybrid Drives Finally Coming of Age? that can be purchased for immediate download from the Objective Analysis website.

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