Apple’s Fusion Drive – a closer examination

24 Oct 2012

Though a bit lost in the excitement of the iPad mini, Apple’s Fusion Drive, which was revealed alongside the new iMac and Mac Mini, is an innovative best-of-both-worlds concept worthy of a closer look.

While hybrid storage is nothing new to some, the Fusion Drive will bring this concept to the mainstream in a way that can be easily understood and adopted.

 A configurable option for the new iMac desktop computer, Fusion Drive eliminates customers’ choice between a hard disk drive (HDD) and solid-state drive (SSD) by giving them both in one. This means users can get either 1TB or 3TB hard drive storage capacity coupled with the fast performance of a 128GB SSD.

How it works

The beauty of this hybrid drive is that the operating system presents it as a single entity and users treat it as one – all the work of deciding which files and applications belong on which drive is dealt with by the operating system. Working in the background, OS X Mountain Lion will keep users’ most frequently accessed files on the SSD, and files that see less use on the HDD.

This is done automatically, with OS X copying the files from one drive to another without any user input required. Even if the user unplugs or shuts down their device during a transfer, the original copy of the file remains and no data is lost. Only when the copy is complete is the original file deleted.

Fusion Drive performance

Writing files is also more efficient as everything is automatically written to the SSD first for faster completion and less impact on computer performance. A 4GB write buffer should accommodate most writes in typical use and, if OS X sees fit, files will be moved to the HDD after writing.

What makes it different

From what we can tell, Fusion Drive isn’t an SSD cache drive or a RAID, based on how the two drives work in tandem with one another. The storage space afforded by both drives is what you get in the combination, so 1TB HDD plus 128GB equals about 1.12TB of total storage. While other hybrid drive options exist out there, Fusion Drive seems to offer the highest capacity SSD available.

But what’s really clever about Fusion Drive is how OS X manages it all. Users have all the benefits of a hybrid drive without having to know the ins and outs or even making any decisions on what files should go where. For the mainstream user, this represents a significant leap forward in terms of fast-performing user-friendly storage options.

That said, how well OS X manages users’ files will have to be road-tested when the new iMacs are released later this year.

Elaine Burke is the editor of Silicon Republic