Attribute disk usage to a directory tree.
du
What is using space in this tree
du -sh * | sort -rh | head
Limit to one depth
du -h --max-depth=1 /var | sort -rh | head
Files large enough to matter
find /var -type f -size +500M -exec ls -lh {} +
Apparent size versus allocated size
du -sh --apparent-size .
du -sh .
The difference is sparse files. A file can report a huge apparent size while occupying little disk.