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][1] 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][2], 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.


  [1]: http://apple.stackexchange.com/questions/136590/how-can-i-delete-a-partition-corestorage-logical-volume-from-the-terminal
  [2]: http://macs.about.com/od/diyguidesprojects/ss/Split-Your-Fusion-Drive-Apart.htm#step1