I'm running a late 2012 iMac running El Capitan with a 1TB Fusion drive. today my iMac froze and was unresponsive so I did a hard restart. After the restart it was not responsive so I did a hard power off. It turns out that it was probably running the latest system update at the time so turning it off the second time was bad. I turned it back on and let it start up for a few minutes. It got to the Apple loading screen, then turned black with the "No symbol" appearing on the screen (verbose start showed it was stuck looking for the root drive). After starting in recovery mode disk utility showed only the 1TB HDD and not the CoreStorage SSD part. diskutil cs list gives the error: "no corestorage logical volume groups found". Nothing I've tried so far (e.g., cat /dev/random > /dev/disk0) has worked. Any suggestions for how to see and 'reattach' the other 128GB Fusion drive so I can get my computer back up and running. Right now it just thinks I have a 1 TB hdd instead of 1.2 TB (which is a problem for trying to restore my Time Machine backup because I was down to about 15 GB free space).