Problem installing Big Sur on I Mac

Thanks for the reply. Here is the information:

Current is version: Mojave 10.14.6

Volume type :         APFS Container

BSD device node :      disk2

Connection :         SATA

Device tree path :      IODeviceTree:/PCI0@0/SATA@17/PRT0@0/PMP@0

Writable :         No

Is case-sensitive :       No

Volume capacity :      3,121,401,434,112

Available space (Purgeable + Free) : 363,098,238,976

Purgeable space :      0

Free space :         363,098,238,976

Used space :         2,758,303,195,136

Owners enabled :      No

Is encrypted :         No

Can be verified :       Yes

Can be repaired :      Yes

Bootable :        No

Journaled :        No

Disk number :        2

Media name :        AppleAPFSMedia

Media type :        Generic

Ejectable :         No

Solid state :         No

SMART status :      Not Supported

When I first ran First Aid it did not complete (no progress bar / “Done” greyed out). Checking the detail window I saw lots of errors, unfortunately I did not record them. The latest First Aid run did not complete, with the spinning disc running continuous. Had to  hit “escape” to stop it. My guess is it must be a hard drive fault. I have ordered a 4tb SSD for replacement next week and hope this solves the problem.

I also tried to install Big Sur on an external USB flash drive, although the installer on the USB seemed to have gone to plan, but when I tried to select it as a “start up disk”, in system preferences, it did not show up as an alternative in the window to start my Mac from. So I am stuck with my old System, meaning I can’t load or run Octane Render.

Thanks for you kind help.