Greetings- I have unraid 7.1.4, Cache drive is Samsung_SSD_850_EVO_250GB. It is continually showing with ~119GB used, but largest actual file is a 28GB movie. Here are steps I took to find/troubleshoot (gleamed from scanning these forums and using GPT):

1. Checked largest files with du — found only ~28GB visible (the movie)

2. Verified no snapshots with btrfs subvolume list — returned nothing

3. Checked for deleted-but-open files with lsof +L1 — found none after Docker restart

4. Ran btrfs balance to defragment — minimal effect on used space

5. Confirmed no hidden mounts inside /mnt/cache

6. Noted deleted docker.img file was once open but no longer exists or held open

7. Ran filesystem scrub — no errors found

8. Performed deeper du scans inside cache — no large hidden files discovered

9. Concluded space usage discrepancy likely due to BTRFS metadata/internal usage or hidden data not visible with standard tools

Any suggestions or troubleshooting steps or videos you would suggest? Thanks community!

If there are any vdisks there they can grow with time, but if you cannot see which file is the issue, you can use the mover to start moving things to the array until you find the culprit, then move back.

Thanks for the suggestion! That was my next step, just wanted to see if there was anything automated I could do.

With btrfs it can be difficult to find the actual cultprit(s), since tools like du and similar are not reliable with it.