Western Digital announced today that it has begun sampling new 5mm-thick hybrid 500GB hard drives designed for use in Ultrabooks. Hybrid drives, which use a small amount of solid-state storage alongside a spinning hard drive platter, are designed to make systems feel speedy while keeping capacities up and costs down relative to "true" solid-state drives.
Mobile hard drives have traditionally been 9.5mm thick, though higher-capacity drives have sometimes ventured up to a slightly beefier 12.5mm. More recently, both SSDs and hard drives have begun to show up in slightly thinner 7mm versions—the Samsung 830-series drives are an example of the former, while we saw a 7mm hard drive from Western Digital itself when we took the keyboard cover off of the Acer Timeline M5 we reviewed. These 5mm drives are the next step in that process—where advancements in hard drive platter technology were previously used only to expand capacity using the same amount of physical space, we're now seeing the technology used to hold capacities steady in a decreasing amount of space as well.
Western Digital hasn't provided any information about the speed or quantity of the MLC NAND flash storage that will be used in the drives, though the fact that MLC flash is being used suggests that it will be comparable to the 20GB or 32GB flash caches seen in many of today's budget Ultrabooks. Drives that use more reliable but more expensive SLC flash, like Seagate's Momentus XT hybrid drives, typically use 4GB or 8GB of flash instead (our own Lee Hutchinson details the differences between the two types of memory here). This would be an interesting development—most of the "hybrid" solutions in today's Ultrabooks pair a standard hard drive with a small, separate SSD installed via an mSATA slot on the motherboard. Combining the two into one drive, as these Western Digital drives purport to do, would further save space in the laptops that use them.
But this is all just conjecture—we'll learn more about the new hybrid drives at the company's Investor Day on September 13. Given that today's announcement, available in full over at Engadget, is just about the company sampling the drives rather than putting them on sale, we would expect these to begin showing up in systems in 2013.
