Need help with fixing Fusion Drive of iMac

DmitryV wrote:

Hello!

i have iMac 27 2019

After reinstall OSX Catalina my Fusion drive been divided into SSD and HDD.

I tried fixing Fusion Drive - reboot iMac in Recovery mode and use the Terminal.

I try command

diskutil resetFusion

It not work for me and give error

Error: -69877: Couldn't open device

I think it is problem with SDD disk (for my Disk0). I try unmount it by command

diskutil unmoutDisk disk0

and give error:

Unmount of disk0 failed: at least one volume could not be unmounted

Unmount was dissented by PID 0 (kernel_task)

What can i do now and how i can to fix my Fusion Drive?

I will be glad of any help.

How to fix a split Fusion Drive - Apple Support