My 2 TB Fusion drive has become a SATA Drive of 2 TB. I have an IMac 27 inch late 2015 with a 2 TB Fusion drive. After an update my computer crashed. I had to install the OS X from the OS that came with the IMac. I have updated everything to OS Catalina 10.15.7 and i use the Time machine back up to restore. But when i started the IMac i noticed that everything was soo slow.. `everything works slow. Opening apps, opening windows...slow. And then i noticed that my Fusion drive was a SATA drive! If u go to about this mac and then go to 'storage'. then u see that it is an SATA drive instead of Fusion. What can be happened? Is this why my. machine is so slow? Does the IMac not see the Fusion drive? ( i can't upload pictures here?..)
A Fusion drive is simply software that presents two separate devices (a small SSD and a large HDD) as one disk volume.
However, it is possible for the drives to become 'split' as their separate components.
It sounds like your Fusion drive was split -- either when you erased and reinstalled after the crash; or possibly if the SSD failed. Do you not see the smaller SSD volume shown anywhere?
It's more usual for the mechanical hard drive to fail -- and I would be concerned about the reliability of a 7-year-old hard drive.
My advice is to get a large external USB SSD, and use that instead.
Before restoring, you needed to fix your split Fusion Drive. Apple has instructions posted at How to fix a split Fusion Drive. Basic steps are given below.
These steps permanently delete all data stored on the drives that make up your Fusion Drive. Make sure that you have a backup before continuing.
If using macOS Mojave or later
- Turn on your Mac, then immediately press and hold Command-R to start up from macOS Recovery. Release the keys when you see the Apple logo or spinning globe.
- When you see the macOS Utilities window, choose Utilities > Terminal from the menu bar.
diskutil resetFusionin the Terminal window, then press Return.
Yes(with a capital Y) when prompted, then press Return.
- When Terminal indicates that the operation was successful, quit Terminal to return to the macOS Utilities window.
- Choose Reinstall macOS, then follow the onscreen instructions to reinstall the Mac operating system. Your Mac restarts from your Fusion Drive when done.