Chosen Solution
My Mac Mini late 2012 came with 1 HDD, I installed an SSD drive in the other available drive bay. After rebooting, both drives are available, but I cannot seem to create a combined fusion drive. I tried reinstalling the OS (El Capitan 10.11.1) but it does not create the single fusion drive. The OS installer will only let me install on the one of the two drives.
Sorry for not getting to you, I needed to do some checking. El Capitan Disk Utility is not as good (complete) as the older Mavericks & Yosemite versions. It appears Apple still won’t let you create a Fusion drive with it with 3rd party SSD’s. But don’t despair! You still can do it you just need to do it using the command line interface. Follow this: How to make your own Fusion Drive. Be aware you will need to do this from an external bootable drive as you can’t do it using the OS on the current drive.
it didn’t work for me. I got: “A problem occurred; undoing all changes Error: -69888: Could’t unmount disk”
