My Mac thinks its drive is full but it's not

[AndrewClarke]

Late 2012 quad core Mac mini. 16GB RAM, MacOS Mojave 10.14.6, 1.5TB Fusion Drive (500GB SSD + 1TB spinny disk)

I'll start up my computer, and within about a day it's telling me the drive is full even though I have about 330GB free. df in Terminal confirms this, and I can't find any indication of any hidden MacOS "feature" filling up my drive. I don't know of any drive problems and I have DriveGenius and DiskWarrior running at the moment.

Sometimes I'll get a message stating that the computer is out of memory (or virtual memory) and that I have to close applications. This time, I didn't get this error but since MacOS is reporting that the drive is full, basically any app that needs to write to the drive is failing.

I'm not using the computer for much, at least not in the "sitting in front of it" way. I've mounted a 5-bay Drobo with DiskWarrior and trying to back it up to a network drive using a combination of rsync, Finder and Chronosync. Plus I'm syncing a Photos library that's about 1TB but 99% of it is already on the drive.

Any ideas on how to troubleshoot what's happening and fix this? Thanks.

 

[HDFan]

If you run a visual disk utility program such as Daisy Disk does it give you any insights?

If you temporarily remove content to clear more space is there a point at which the problem goes away?

There are a number of OS tasks that use temporary files, Time Machine being one of them.

 

[Fishrrman]

Do you use Time Machine?
Could your internal drive be getting full of "local backups" or "snapshots" (or whatever they're called, I DON'T use tm)?

Also...
Check activity monitor and see if any processes are "running away" on you. They could be producing "temp files" over and over and over and over and over, etc.

 

[AndrewClarke]

Thanks. I've never used DaisyDisk, but I've used GrandPerspective and OmniDiskSweeper. GP doesn't seem to show unused space, and OmniDiskSweeper did show me something really odd. My Photos Library is ~1TB but both of the aforementioned apps actually seemed to miss that entirely. I installed DaisyDisk, tried it unregistered, paid for it, and by the time I went to register my version of it, my drive was reporting full again and the registration won't save on my drive until I reboot my computer again.

Thing is, my drive reports 330GB free everywhere I can look. Terminal, Finder, Disk Utility, etc. I do have 3 local time machine backups when I run a "tmutil listlocalbackups /" but I've tried turning off Time Machine and that doesn't make a difference. Plus my backup drive array is always plugged in and it backs up every hour, until I "run out of disk space" on my Mac, that is.

In any case, if my drive was actually full, it should show as full. The only other thing I can think of is that I have FileVault turned on. Maybe it's running into a problem clearing up space, or something along those lines. I have an up-to-date backup, so maybe I'll try turning that off and see what happens.

 

[AndrewClarke]

I've given up on this. I bought a 2TB SSD and I've stuck that into the Mac mini. Out went the 1TB spinny disk and along with it the Fusion drive.