On the Fusion Drive

Since publishing my article about tech that should come to the Mac this morning, I’ve gotten a lot of feedback about Fusion Drives.

For the uninitiated, the Fusion Drive is a storage solution Apple ships with the Mac mini and iMac that uses a small SSD mated to a larger spinning hard drive. To vastly oversimplify what’s going behind the scenes, the system sees these two devices as one volume. OS X, core apps and the user’s most-used files are on the SSD, while apps and data accessed less frequently live on the hard drive.

This system is designed to give the user the best of both worlds: SSD performance with the large capacity offered by cheap spinning disks. In practice, most users will see speeds much closer to what an SSD can provide than users without a Fusion Drive.

It’s not all great news, though. Fusion Drives generally work well, but there is a level of complication to them not found in single-device storage systems.

Then there’s the penny-pinching. In late 2015, Apple adjusted the Fusion Drive to include much less Flash storage space on some models:

In previous versions of the Fusion Drive, Apple has included 128 GB of flash storage—enough to store a lot of large apps and files that you use frequently. In the new iMacs with 1 TB Fusion Drives, however, that number has been cut to an insanely small 24 GB.

This means that less can be on the SSD at any given time. While OS X and many core apps will still fit there, more users will have more files on the spinning hard drive more of the time, making the overall experience slower than it may have been previously.

SSD costs are still higher than hard drives, so the Fusion Drive continues to exist as a stop-gap. Many users need bigger capacities than Apple offers in their all-SSD models. Other users simply can’t — or don’t want to — pay for a 1 TB SSD at Apple’s prices.

I wish we could move past the Fusion Drive and live in all-SSD world, but I fully realize why we aren’t there yet. But hey, it’s fun to talk about goals.