Western Digital has announced a new 2.5-inch single-platter hard drive that's a scant 7mm thick, aimed squarely at ultrabooks. Available in 500GB and 320GB storage capacities, Western Digital claims that the new drives are shock resistant and very energy efficient — the new drive reportedly consumes a mere 1.4W of energy while under load; the older, 9.5mm variant consumed 2.5W. That's a nice complement to the all-day battery claims ultrabook manufacturers are trying to hit.

There's that little matter of performance: the 8MB cache and 5,400rpm speed are about average for notebooks, but those specs are absolutely crushed by a solid state drive — the standard equipment for any ultrabook worth its salt. So what gives? That price tag, to start: The 500GB model sits at a cool $100; solid state drives with comparable capacities start at $500, and only get pricier.

You can expect to see these drives appearing in lower-cost ultrabooks, or available as an option for consumers looking to cut costs. It's a bit antithetical to the entire notion of the ultrabook, but not a terrible tradeoff; if you're more concerned about saving some cash than seeing bleeding-edge performance in your cutting-edge laptop, you could do worse.