I have 16 GB system drive for openmediavault which is reporting 98% full
# df -h /dev/sda2
Filesystem Size Used Avail Use% Mounted on
/dev/sda2 15G 14G 346M 98% /
However disk usage is only 2.5 GB
# du -d1 -x -h / | sort -h
Where are the rest 11,5 GB that it's reporting used?