hard drive – Can’t free up purgeable space in macOS 11.3

I’ve ran into this problem where my external Thunderbolt volume, which is formatted with encrypted APFS is not letting me free up any space, regardless of what I do.

When I first noticed, I manually went in and moved about 100GB from the drive in question to another location in order to free up space. However, when I went to save new stuff to the volume, it once again complained it was out of space.

This is what’s being reported in DaisyDisk:


This is what df reports:

Filesystem       Size   Used  Avail Capacity iused       ifree %iused  Mounted on  
/dev/disk3s1    1.8Ti  1.8Ti   39Mi   100% 2603571 19530493869    0%   /Volumes/2bigRAID

If I run du on the disk, it reports a total of 880G (the disk is 2TB).

I’ve tried the following:

  1. Used the CleanMyMac “Clean purgeable space” feature
  2. Rebooted in recovery mode and ran First Aid on the disk
  3. Made sure trashes are empty

All to no avail. I can’t add any new files to this disk. I’m borderline considering making a copy of everything to another drive, re-formatting this one and then moving things back. But, it’s an SSD and I’d rather avoid the unnecessary write cycles if there’s something else I haven’t considered.