One of the downsides of having an Ultrabook is that you often don’t get a whole lot of storage space to work with. Sure, you save on physical space with the svelte machines, but actual storage for your digital wares is usually limited to sizes under 256GB. But that could soon be a thing of the past.

This week, Western Digital is talking up a development that aims to bring larger drive capacities to thinner laptops with slimmer hard drives.

Previously, notebook hard drives have measured 9.5mm thin, which puts them roughly on the same thickness as many smartphones. This year, WD started shipping out smaller drives, measuring 7mm thick for ultra-portables, but the storage maker may have actually out-done itself again with a 5mm hard drive.

To put that into perspective, the new 5mm internal notebook hard drive is actually a hair thinner than Apple’s new iPod Nano, a media player that is the thinnest yet for the company.

“Mobile devices are becoming smaller, thinner, lighter and more responsive,” said Western Digital’s Matt Rutledge, Vice President of Client Storage Solutions. “Working with our technology partners, WD has developed new 5 mm hard drives that enable high capacity storage along with excellent performance and superior economics to allow our customers to expand their thin offerings.”

The drives will pair solid-state drive technology with conventional hard drive technology, offering 500GB of storage with an element of static memory, enabling them to be faster and utilise less power, which is perfect for the type of computer the drive is aimed at.

You can probably expect to see these new drives in Ultrabooks from next year, with Acer and Asus two manufacturers looking at bringing the 5mm drive technology to notebooks.