Presented as a single volume on your Mac, Fusion Drive automatically and dynamically moves frequently used files to Flash storage for quicker access, while infrequently used items move to the high-capacity hard disk. As a result, you enjoy shorter startup times and—as the system learns how you work—faster application launches and quicker file access.

Fusion Drive manages all of this automatically in the background. And it comes already set up, so you don't have to do anything to make it happen.