imac - partition lost / can't use

[Cluberrlang]

I've have a 3tb fusion drive on imac that I had partitioned as a 2.45tb drive and a ~500gb other partition, when I was formatting the larger one the computer froze and I had to force shut down. That 2.45 drive is now not showing up at all. I've tried fresh installs, ran recovery mode and tried to format it from Disk utility there but no luck. I've put some screenshots there and I'd really appreciate any help at all!

 

[hobowankenobi]

It's been years, but I have seen drives die if a formatting/partitioning function would not complete, and was force quit. I have assumed when it happened the drive was already having a mechanical issue...and the operation pushed it over the edge.

Could be the case here.

OTOH, unless you have any data on it that you must recover or preserve, I would consider trying to reformat, but not as a Fusion drive....so you really test the drive, not just the volume. Breaking it apart takes a few steps.

 

[Fishrrman]

Do you have access to another, working Mac?
If you do, try this:

1. Get a USB flash drive 16gb or larger.
2. Install a clean copy of the OS onto the flashdrive (do not make it "an OS installer". Instead, set it up as a working Mac drive that you can boot to the finder).
3. Put a basic account on it. Again, you want a USB flash drive that is bootable to the finder.
4. Take it to the problem iMac.
5. Boot the iMac from it.
6. NOW open Disk Utility, and see if DU can "see" and re-initialize the internal drives.

Note:
DU may see two drives inside, because that's what's there (SSD portion and HDD portion).
If it was me, I'd re-initialize each of them and "let them be" as "standalone" drives, and go on from there.