How to make room on a non-primary boot drive?

[T Coma]

I'm helping a relative with a crashed 2017 iMac with a 2TB internal SSD, professionally replaced over a year ago. It would get stuck on the boot screen, and would boot very slowly in safe mode. Before asking me for help, they decided to try and install Big Sur over the existing Mojave to try and alleviate the problem - I don't know if the install was successful, but it still wouldn't boot. I created a Mojave boot drive off an external USB3 drive and restored from Time Machine. I ran the usual scans and checks and found no apparent damage or corruption, but I noticed that there is almost no space left on the drive, so I'm wondering if the space issue is what's causing the boot problem.

I figured I would delete some big video files and see if the space was the issue, but I only hit delete and not option-command-delete so I guess they went to the local trash bin? Unfortunately I can't find that trash bin in finder now, and the SSD doesn't show any change in space available. The trash can is empty on the external boot drive.

Any ideas on how to find them?

 

[jz0309]

since you seem to have a backup, I'd go and erase the drive and start from scratch ...

 

[KeesMacPro]

As recommended start with a clean Mojave install on an erased ssd.

You could run DriveDX to check the health of the drive.

I noticed that there is almost no space left on the drive

It's necessary to keep at least ~20% space free (in this case: 400GB) for an SSD to work fine.
TRIM also should be enabled manually for 3rd party SSDs : open terminal and type: sudo trimforce enable

I only hit delete and not option-command-delete so I guess they went to the local trash bin? Unfortunately I can't find that trash bin in finder now

Depends on the settings in Finder e.g. when I hit command+delete the trash bin is emptied permanently.

Another thing is that running Mojave and up (APFS format) more space available isnt immediately shown when something's deleted. Normally after about 2-3 days the disk free space shown is correct.
This is a short version, but you may google it and will find the exact explanation.

 

[T Coma]

I ended up reinstalling Mojave on the SSD and backing up from their most recent TM... which apparently was from January. So anything new on the system between January and now was lost... except that I cloned the SSD to a 5TB external HDD. So I fired up Migration Assistant to copy that missing data back over via USB3 and it says

I don't know what is up with that Xfer speed. Yes it's an HDD but a new one and it's USB3.0. It didn't take half that time to run the Time Machine backup.

 

[T Coma]

speed kept going down - couldn't backup from Time Machine or Migration assistant. Odd if drive is failing - it is acting exactly like the SSD (98% life left, and no problems according to Drive DX). I have read some bad experiences here and elsewhere related to Mojave and HPFS or Journaled discrepancies. Or something like that. Whatever it is, I'm manually bringing files over, one folder at a time. PITA