Fusion Drive: Restore from Time Machine - "The disk can't be erased."

I'm having a very similar problem. And even if I freshly destroy and then recreate the Fusion drive on this 2015 iMac, Time Machine Restore still wants to reformat the volume AGAIN. And it fails because it cannot. How do you solve that specific problem? If I could suppressed time machine's need to erase a drive before it restores, that would do it, but I don't know how to do that. Or of course if apple would built into it's own software, the ability to manage and create and destroy fusion drives, that would also help quite a bit.

Apple has not provided an easy way to recover from this condition. If you don't feel able to carry out these instructions, please get someone more experienced to help you. One option is to make a "Genius" appointment at an Apple Store.

Start up in Internet Recovery mode by holding down the key combination command-option-R at the startup chime. Release the keys when you see a spinning globe.

Note: You need an always-on Ethernet or Wi-Fi connection to the Internet to use Recovery. It won’t work with USB or PPPoE modems, or with proxy servers, or with networks that require a certificate for authentication.

In the OS X Utilities screen, select

Utilities ▹ Terminal

from the menu bar at the top of the screen—not from any of the items in the OS X Utilities window.

Follow the procedure in this ASC thread to split up the Fusion Drive. The long string of letters, numbers, and dashes that you will have to enter will be different in your case. Copy and paste it from the Terminal window into the command.

This operation will remove all data from the Fusion Drive, so you had better be sure of your backups.

Quit Terminal, then repair the Fusion Drive (see under "Troubleshooting" on the linked page.)

Quit Disk Utility. You should then be able to install OS X and restore your data from a backup in the main screen.

That's right.

The instructions that I posted earlier are not as clear as they could be, so I'm posting what I hope are clearer ones below for the benefit of anyone else who might find this thread.

Apple has not provided an easy way to recover from this condition. Please read this whole message before doing anything. If you don't feel able to carry out the instructions, get someone more experienced to help you. One option is to make a "Genius" appointment at an Apple Store.

This procedure applies only to an iMac or Mac mini with a factory-installed Fusion Drive.

You'll need to refer to these instructions while no web browser is running, so either print them or load them on another device before you begin.

1. You need at least two complete, independent backups of all data before proceeding. One backup is not enough to be safe. There are ways to back up a computer that isn't fully functional. Ask if you need guidance.

2. Disconnect all external storage devices.

3. Start up in Internet Recovery mode by holding down the key combination command-option-R at the startup chime. Release the keys when you see a spinning globe. Select a language, if prompted.

Note: You need an always-on Ethernet or Wi-Fi connection to the Internet to use Recovery. It won’t work with USB or PPPoE modems, or with proxy servers, or with networks that require a certificate for authentication.

4. In the OS X Utilities screen, select Get Help Online. Safari will launch. While in Recovery, you'll have no access to your bookmarks, but you won't need them. Load this web page.

5. Triple-click anywhere in the line below to select it:

diskutil cs deleteLVG `diskutil cs list | awk 'NR==3{print $NF}'`

Copy the selected text to the Clipboard by pressing the key combination command-C.

6. Quit Safari. You'll be returned to the OS X Utilities screen.

From the menu bar, select

Utilities ▹ Terminal

The Terminal application will launch. Paste into the Terminal window by pressing the key combination command-V. Wait for a new line ending in a hash sign (#) to appear. Quit Terminal to be returned to the main screen.

This operation will remove all data from the Fusion Drive, so you had better be sure of your backups.

7. Now you can repair the Fusion Drive (see under "Troubleshooting" on the linked page.)

8. Quit Disk Utility. If you have a Time Machine backup, connect the backup device and restore your data in the main screen. If you backed up to a network device such as a Time Capsule, it should be connected automatically.

9. If you don't have a Time Machine backup, or if you can't restore from the Time Machine backup that you do have, install OS X. You'll restore the data later.

In Internet Recovery mode, you'll be installing the original version of OS X that shipped with the machine. If you've upgraded the OS in the App Store, and you want to install the latest version, then restart in local Recovery mode by holding down the key combination command-R (not the option key) at the startup chime. When you install the OS, you'll be prompted for the Apple ID and password that you used to upgrade.

It looks like you did what you had to do, but the machine isn't responding the way it should. That makes this a warranty issue.

The warranty entitles you to complimentary phone support for the first 90 days of ownership.

If you bought the product in the U.S. directly from Apple (not from a reseller), you have 14 days from the date of delivery in which to exchange or return it for a refund. In other countries, the return policy may be different. If you bought from a reseller, its return policy applies.

Nothing in your response suggests that you can't take advantage of the phone support that you paid for.

This is the second storage-related failure you've had with the machine. It's defective. There is no point in trying to hack data onto it, in my view. If you're within 90 days of purchase or have AppleCare, you may be able to arrange for on-site service.

What did Apple Support tell you when you called?