Catalina 10.15.7 update bug or dying HDD?

[RojoPantalon]

Hey all, having a bit of a nightmare since trying to install 10.15.7 and looking for some advice.

The Problem
My Mac mini late 2014 seemed to be working fine, it was slow, but it worked. It then automatically tried updating to 10.15.7 and the update froze leaving my Mini in a boot/fail/boot loop - I also couldn't boot into safe mode (would just restart endlessly).

I tried using recovery mode and repairing the disk, but when repairing the 'data' portion of the disk, Disk Utility would freeze.

I then tried recovering from a Time Machine snapshot which worked. I've since tried repairing the disk again, but no dice.

So I'm thinking my Catalina install might be corrupted, so I use internet recovery and attempt a clean install - I leave it for 24hours but it's stuck on 'estimating time remaining' - I reboot, install restarts, same problem - here we are another 36hours later and it hasn't moved.
So time to boot into recovery again in the hopes of cancelling the loop and going back to square one.

Diagnosis & Solution
Any ideas on what might be the issue? I'm thinking either - the failed 10.15.7 has corrupted my disk - OR worse, my HDD has been on its last legs for some time and I'm only just seeing it now, I'm hoping this isn't the case, as aside from Disk Utility not working and this update failing, it seems to be working.

Should I try making a bootable USB? Or does anyone have any other ideas?

The Twist
Funnily enough, before this started I ordered an SSD blade which I planned to install myself and use as a fusion drive together with the HDD - which is essentially the main thing I want to accomplish (its used as a home media box)
Is it worth installing OSX on the SSD blade, installing that in the Mini and then booting from there in an attempt to reformat? I'm thinking if my HDD is dead and needs replacing, I'd rather not open up the Mac mini twice.

Does anyone have any recommendations? Is there any way of mounting my Mac mini's drive on another Mac (like you used to be able to do with firewire) and repairing/diagnosing/reformatting from there? Any suggestions are very welcome.

 

[Honza1]

In my experience with 2017 MBP the disk or other hardware is likely bad and there is not much help. Now, in my case it was SSD, so take it with grain of salt. But my disk slowed down and when I tried to run Disk Utility from recovery partition, it hanged. I got help and we tried everything, including to reformat the SSD. That crashed the computer also (rebooted). Apple replaced mainboard with the SSD (which is soldered in in this case) under AppleCare warranty.

 

[brianmowrey]

Well, I don’t see in your notes that you’ve tried a clean reinstall? Seeing whether formatting the HD in Recovery Mode Disk Utility (going to All Devices view to show the disk itself) is successful, and if First Aid gives the drive/container/volume a pass afterward would be interesting. That said, your successful Time Machine restore with no improvement to updating afterward suggests that the reformat/reinstall process would also be a fail.

If you are finally convinced the drive is broken, just replace the drive. HD upgrades in 2011-2014 era Mac Minis are complicated but not at all messy or skill-intensive. I had a lot of fun when my native Mini HD failed.

 

[RojoPantalon]

Well, I don’t see in your notes that you’ve tried a clean reinstall?

I tried doing it very internet recovery as you can clean install from there. However do you think it's worth making a bootable USB and trying that way?

Or just reformatting in recovery with disk utility?

 

[brianmowrey]

Or just reformatting in recovery with disk utility?

That’s what I meant by clean install. If the reformat and subsequent first aid on volume/container/drive fails, that’s a strong sign that replacing HD is the way to go - but it also might break your current Time Machine restore function and leave you with nothing until the HD is replaced

 

[RojoPantalon]

So quick update. I've wiped and reformatted the disk as suggested. Worked ok and First Aid not picking up any issues.
Only weird thing is, even after wiping it's showing 500GB of 'Other volumes' taking up my 1TB disk? Not sure wtf this means?


Now reinstalling Catalina, let's see what happens. Fingers crossed.

 

[brianmowrey]

even after wiping it's showing 500GB of 'Other volumes' taking up my 1TB disk? Not sure wtf this means?

Weird - I wouldn't consider that a successful reformat. This was after using All Devices view to make sure you were formatting the drive itself? It might be time to go from Disk Utility to Terminal at that point; which is the point I would consider myself defeated. Or I would try a level 1 secure erase in case that magically worked better than normal reformat.

I missed the nuance of your planned SSD add-on before; now I get the part about trying to really pin whether the current HDD is healthy to avoid opening the Mini twice. That does muddy up the decision-flow. But I still say don't be afraid to jump the gun; HDD replacement on the Mini is a fun Lego project.

 

[RojoPantalon]

So good news - figured out the 500GB of 'Other volumes' thing - or at least solved it with an additional reformat of the entire disk - rather than just the APFS volumes (counteracting Apple's own guidelines but it worked).
Catalina seemed to install without a problem - given all looked good I also went ahead and installed the SSD blade and merged the drives into a Fusion drive.

So far so good. I've now restored from my Time Machine back up and no complaints so far.
Can only assume my HDD is in fact healthy and that Catalina (and years of OS upgrades since Snow Leopard) may have caused the issue I experienced. So for any others that experience this - clean install seems to be the way to go over updating.

Bonus: the SSD has sped things up nicely, hoping it will only get faster as the Fusion drive figures out which files get used the most.

Thanks for all the help and advice!