Still can’t install Big Sur

Update: APFS was the culprit. When I tried First Aid on the drive, Hard Disk Utility kept telling me that it couldn’t help: “NX media keylocker data range is invalid” and “Container superblock is invalid”. Both of these errors appear to have something to do with the introduction of APFS a couple of Apple Systems ago (Google it).

I made a bootable USB drive with the Big Sur installer (https://support.apple.com/de-ch/HT201372 - apologies this is German), selected that drive as the startup drive, used Hard Disk Utility to format the Fusion drive, and then installed Big Sur... now I’m restoring my user data and programs from the Time Machine backup.

Pretty ugly update path, I must say. Well, problem solved, anyway. Maybe this will help someone else.

Thanks, but space is not an issue here. The Fusion Drive is a 200 SSD / 800 Hard drive. There is > 350 GB free space on the machine. If there weren’t enough space, the installer would note and show a message.

The Fusion Drive is one drive to applications. The fact that part of it is an SSD, and another part of it is a regular hard drive, is transparent to apps. I have no separate SSD partition. The OS takes care of moving stuff between the hard drive and the SSD, but that is not visible to apps - or to me (as the user). The drive has >350 GB free (=empty space). If Big Sur would not find enough space on the drive, regardless of where that space is physically located, it would complain about not enough space.

Thanks!

I am currently running Catalina and that’s what I ran Onyx on, prior to my attempts at installing Big Sur. So no, I can’t have damaged my installation with Onyx.

I was also thinking that multiple restart might be ok, but after the first restart, when it’s showing the Apple logo and a progress bar and nought else, it’s restarting every 1:53 minutes... for ever. I stopped this after about 30 restarts, every one at 1:53, punctually as a clock, which no firmware update on the planet would require.

As there are quite a number of people with problems installing Big Sur, I think I’ll wait for the first update, download the installer again, and try again... if that doesn’t help I’ll call support.