What is a Fusion Drive?

Fusion Drive is Apple’s name for a hybrid storage drive consisting of a hard drive and a solid-state drive. Solid-state drives have higher performance than hard drives and by combining the two it increases the overall performance.

How does it work and what are the benefits?

macOS combines these two drives so that to the user it appears as a single drive. Most commonly accessed files are dynamically allocated to the solid-state drive portion of the drive, whereas less commonly accessed files are kept on the hard drive portion. This way the faster solid-state drive’s better performance is efficiently leveraged.

 A practical example of this would be that all of the operating system files are stored on the solid-state drive to reduce loading times when booting or opening applications.

 In addition to the increase in performance, as solid-state storage is relatively expensive compared to hard drive storage it allows for a cost effective way to have a faster drive with a large amount of storage space without it being prohibitively expensive.

Which models have Fusion Drive and how do they differ?

The Fusion Drive was offered as an option with the introduction of the Late 2012 iMac and Mac mini, it has not been offered as an option for the MacBooks. From the 2017 model year the 27-inch iMac offers the Fusion Drive as standard.

The size of the solid-state drive component can differ depending on the machine, model year and overall size of the Fusion Drive, the configurations are shown in the table below.

Mac mini

iMac 21-inch 

iMac 27-inch  

For a deeper, technical dive on Fusion Drive check out this article from Ars Technica, “Achieving fusion—with a service training doc, Ars tears open Apple’s Fusion Drive”