How to find the directories that are occupying the most space on the system?

The below command will list the 15 directories with the highest disk usage. The -x option will make it only search the root file system and ignore any other mounted systems specially ZFS pools, as scanning them may take long time and affect the performance.

du -xh / 2>/dev/null | sort -h -r | head -n 15

If you would like to check for a certain pool, you can replace "/" with "/Your-Pool"