External SSD Space Disappearing - Ghost Volumes?

[ItsAShaunParty]

Monterey 12.6
iMac (Retina 5K, 27-inch, 2020)
3.8 GHz 8-Core Intel Core i7
72 GB 2133 MHz DDR4

I have two external USB-C M.2 SSDs. They are 2 Tb each. Both have the same issue -- They have approx. 1 TB of space missing.

See the first image below.

To clarify, I've never partitioned these drives. And they were showing at full capacity a few months ago.

When I try to run a repair, I get an error that reads:
"First Aid could not unmount one of the other volumes in the volume’s container. Click Done to continue."

I had read in an old post somewhere that sometimes Spotlight can run rampant and start dividing up an external drive, creating "ghost volumes." Maybe it is something like this?

I guess there's an invisible partition on there somewhere? How do I get rid of it without reformatting the disk? IS that possible? Also, why is this happening

THANK YOU!

 

[Fishrrman]

Download DiskWave from here:

DiskWave Homepage

It's small in size and free.

Open DiskWave and go to the preferences.
Put a checkmark in "show invisible files".
Close preferences.

The DiskWave window shows you all your volumes and drives in plain English (no ridiculous graphical formats).
Click on any item "on the left".
Now, you'll see what's ON the volume, listed in order of "largest to smallest".
You can easily locate what's eating up your space.

 

[Brian33]

When I try to run a repair, I get an error that reads:
"First Aid could not unmount one of the other volumes in the volume’s container. Click Done to continue."

Yeah, that is weird. I seem to remember when Monterey first came out there were bugs in First Aid, but I'm pretty sure they've been fixed by 12.6. You can try to manually unmount the volume(s) and re-run First Aid.

In Disk Utility, I'd go to the View menu and click "Show all Devices". This will show you the Containers as well as Volume Groups and physical device names; you can check for multiple volumes within a Container. Currently your Disk Utility is only showing Volumes.

When you click on a line in the left pane, pay attention to the second line in the right pane, just below the large bold-faced line. It will tell you what type of object you're looking at. See if the organization makes sense.

I'd also click "Show APFS Snapshots". If your external volumes are formatted APFS it's possible that your "missing space" is being used by APFS snapshots. Snapshots can be deleted, though the space freed up can be confusing; I recommend deleting the oldest snapshot first and working your way forward.

I do not trust Finder's numbers -- I've seen them be way off. Use Disk Utility, 'du' and 'df').

In Terminal.app, 'diskutil list' will show you all partitions and containers on all your devices, including hidden partitions like the EFI partitions) and hidden volumes (like Preboot and VM on your boot (synthesized) drive). But it's a bit difficult to interpret -- don't do something rash without really understanding what it's showing you...