I have a 2014 iMac Retina running OS X Yosemite and a 3TB Fusion drive. I am attempting to restore it from a Time Machine backup, but when I try to do so, I get the error message, "The disk can't be erased." referring to the Macintosh HD Fusion drive. Trying to use disk utility to delete the drive also doesn't work.
I had previously had this problem when I had to restore my computer, and managed to use the solution found here using Terminal to manually delete the Logical Volume Group. However, now when I use the command:
diskutil cs deleteLVG UUID
The process begins and says "Destroying Logical Volume Group" but it only gets to 20% and then nothing happens. Even after letting it sit for hours it shows no further progress.
I also found this solution here, which recommends using the command
diskutil cs deleteVolume UUID
to delete the Logical Volume first, prior to deleting the Logical Volume Group, but when I do so I get the following message:
Error: -69779: Unable to delete the CoreStorage Logical Volume
So at this point I'm stuck. If anyone has any other suggestions for how I can delete the Fusion drive and restore from my Time Machine backup, I would appreciate any help. Thanks.