1. I have a 5K Retina iMac. Its internal drive is an SSD.

2. It's not working. Let me explain.

3. I booted off an external drive.

4. When I look at the drive in the Disk Utility, there's no option to erase it.

5. When I look at the Partition tab, everything is grayed out.

6. When I click on Verify Disk, it says everything is good.

7. When I repair the disk it says it's all good.

8. The disk does not show up on the desktop.

9. Software cannot see it.

10. I want to format the drive. How?

The fix is in!

Update: Problem solved in the Facebook thread.

Bonus: A video of me fixing the problem, in case you have the same thing wrong with your Mac fusion drive.