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What’s the deal with Apple’s Fusion Drive?

In our review of the latest Apple Mac mini, we talked about the machine’s new Fusion Drive and how it makes the Mac mini better. Apple's new iMac desktops also come available with Fusion Drive. It's £200 extra on the Mac mini, so that's a significant feature that can push the price of the system from £679 to £879 in a heartbeat. So what makes it so special? Here are five things you should know about the Fusion Drive.

What the Fusion Drive is

The Fusion Drive is a combination of Flash storage and a regular hard drive. Flash storage, the same sort of non-volatile memory chips that you'll find in solid-state drives (SSDs), are rugged and much faster than traditional spinning hard drives. But on a pound per GB basis, Flash storage is expensive. That's why the entry-level MacBook Air and other systems that use Flash storage (like tablets) have relatively small storage spaces (64GB to 128GB Flash/SSD vs. 500GB to 1TB for hard drives).

What the Fusion Drive is not

Do not confuse the Fusion Drive with a cache or hybrid drive. Cache drives, like Intel Smart Response Technology, are found in performance desktops as well as many of the latest Ultrabooks. Caching uses a small amount of SSD or Flash storage (16GB to 32GB is common) to help speed up repeatable tasks like booting and waking from sleep.

The cache drives are invisible to the user, and don't count as "real" storage. (A 1TB 5,400rpm hard drive plus a 32GB mSATA SSD yields 1TB of storage). It's the same with self-contained hybrid drives like the Seagate Momentus XT. The Fusion Drive shows as 1.12TB of storage space, which is the 1TB hard drive plus the space from the 128GB Flash storage.

You never have to manage it

The Fusion Drive is set up at the factory; you never have to fiddle with any settings. The drive automatically moves often-used programs and files from the hard drive to the Flash storage and back, depending on how often you use an item. If you ever have to reinstall the operating system, OS X Mountain Lion (10.8) and future versions will automatically set up Fusion Drive for you, even if you need to reformat your main drive.

It makes booting and loading stuff fast

The system files and most of the rest of the operating system will always be on Flash storage, so the system will always boot up quickly. Most of your oft-used applications will reside in Flash, too. That way you won't be sitting there waiting for Adobe Photoshop or Premiere to load: It should come up in seconds.

Fusion Drive optimises documents, too

Do you have a group of templates that you always use? OS X will recognise that and put those documents in Flash. Theoretically, if you like to start every hour with Psy's "Gangnam Style," OS X should recognise that too, and put the AAC or MP3 file in Flash. You never have to remember where your files are, they will appear in your "Macintosh HD" whether the files are physically in Flash or on the spinning hard drive.

So, is Fusion Drive a must-have? We're not entirely sure yet, since we're going to test that further in real life (stay tuned), but if you have the extra £200 in your budget and you're real impatient, it would be an idea to at least consider the Fusion Drive when you configure your new Mac desktop.