If your Fusion Drive appears as two drives instead of one in the Finder, it’s no longer working as a Fusion Drive. Here’s how to fix it.
Fusion Drive, a storage option on some iMac and Mac mini computers, combines a hard drive and flash storage in a single volume for improved performance and storage capacity. If your Fusion Drive appears as two drives instead of one in the Finder, it’s no longer working as a Fusion Drive. This can happen after replacing either drive of your Fusion Drive, or using software to intentionally split them into separate volumes.
You can continue using the two drives independently, or follow these steps to regain the benefits of having the single logical volume of a Fusion Drive.
It’s hard to believe that Apple relied on the Fusion Drive for as long as it did — especially in the iMac. In hindsight, it’s clearly such a weird bridge between two eras of technology.