After failed Big Sur upgrade and manual High Sierra installation, I have two disks : "Update" and "iMac_SSD - Data". How do I fix this?
Hi guys,
I am coming to you to ask for your help.
I own an iMac (Retina 4k, 21.5-inch, late 2015
Processor 3.1 GHz Intel Core i5
Memory 8 GB 1867 MHz DDR3
Graphics Intel Iris Pro Graphics 6200 1536 MB)
It must be said that 4 years ago, I brought my iMac in a specialised store, where they changed the main drive (which was slow and sometimes unresponsive), to an SSD drive.
Because I am stupid, I’m unable to remember exactly which OS I was running before the problem happened.
Anyhow, basically, at some point, in a rush leaving for work and trying to turn off my computer, I accepted some update: upgrade to Big Sur.
After that, I was unable to restart my computer: it gets stuck at the loading screen (I tried leaving my iMac on for 48 hours, just to make sure it wasn’t the installation that was taking some time). I tried recovery mode (first aid on both the drive, which I think were iMac_SSD and iMac_SSD - Data ; reinstalling big sur) but to no avail.
I created a bootable installer with macOS Catalina. Unfortunately, I was unable to install Catalina (the iMac_SSD wouldn’t appear in the disk I could install Catalina on). I read somewhere that it was because I needed an APFS-compatible OS.
I created a new bootable installer with macOS High Sierra. Which - sort of - worked. I got asked if I wanted to install High Sierra on the disk “Update” or the disk “iMac_SSD - data”.
I chose the "Update"-disk and it installed High Sierra. Now, I see in the finder “iMac - SSD - Data”. I managed to save most of my data from “the iMac_SSD - Data” drive, on an external drive.
Now I am wondering what to do. How do I reset everything and do a fresh install? I feel like the Big Sur upgrade split my disk in two, with this weird “Update” disk, and the other “iMac_SSD - Data”.
If I go in the Disk Utiliy, I see two internal disks:
"Update" (1.05 TB ; "shared by 5 volumes"), which has 11.85 GB used, 703.36 GB other volumes, 337.45 GB Free. Screenshot 1 ; Screenshot 2
"iMac_SSD - Data" (1.05 TB ; "shared by 5 volumes"), which has 681.57 GB used, 33.63 GB other volumes, 337.45 GB Free. Screenshot 1 ; Screenshot 2
Is there anyway to fix everything while keeping my data? If yes, how?
If not, how do I reset everything ?
Many thanks if you can help me, this would be greatly appreciated!
iMac 21.5″, macOS 11.6