As a fan of BTRFS, I love doing snapshots to keep things arranged during updates. FreeNAS offers ZFS which should do the same. Tested, works and good for backing up my Mac using TimeMachine. Things went smooth until the disk got a little filled up:

# df -h
Filesystem     Size    Used   Avail Capacity  Mounted on
timemachine       39G     39G      0B   100%    /mnt/storage/timemachine
# rm somefile
rm: somefile: No space left on device

Short and sweet: We’re really doomed now. The Disk is filled up and we are unable to delete even a single file.

And now? Reformating? Geez – Thanks, I still need my data.

The solution is pretty weird, but simple – overwrite a file:

# echo "" > somefile 

… and we got some space for using the rm command again.