Hard disk When it comes to storing all the digital data we create or acquire, the hard-disk drive (HDD) has become the de facto medium we all rely upon. Whether that data is stored on PC, set-top box, games console, NAS device or USB drive, or even in the cloud, the HDD remains the storage that runs the world.

Commanding a price premium is the solid-state disk (SSD). For mobile computing especially, this shock-proof technology makes sense. It's more compact and comes with enormous performance advantages too - an SSD can write or read data faster than a full-size server Raid array, and consumes less power and generates less heat than an HDD.

When netbooks first appeared, flash storage was central to the concept, making for a tougher portable. HDDs crept in when laptop makers started installing Windows, which demanded more space, at a time when affordable flash storage was limited in capacity.

With a bigger budget to work with, Apple has fitted an SSD in even its cheapest MacBook Air, resulting in a relatively accessible high-end ultraportable/expensive netbook.

Most smartphones include several gigabytes of Nand flash, or make provision for adding storage with flash cards. For some Android phones and tablets, though, like the ViewSonic ViewPad 7, you’ll need to find your own microSD card.

Ten years or more ago, the optical disc was king of capacious storage. First CD-ROM, then DVD-R, was used to store data. After the introduction of blue-laser technology, the Blu-ray Disc (BD) became an option for data storage on optical media. The problem for Sony and its partners is that the consumer isn’t that interested any more.

The BD hardware has remained too expensive to entice the price-conscious, the blank discs are 10 times the price of DVD-R, and the burn process is - by the standards of HDD and SSD tech - truly glacial. More crucially, though, is the write-once nature of most optical discs.

There is one new breakthrough to expand the BD format: BDXL. This technology uses three or four layers to provide 100GB or 128GB capacity. It's just as slow and more expensive than ever, though. Read our review of the Pioneer BDR-206MBK for more on the BDXL breakthrough.