Fun fact: pg_dump -Fc on a 110+GiB DB (pleroma's DB), different levels of compression:
0: probably same size as database, didn't stick around to find out, it did pass 20GiB mark VERY quickly.
1: ~15GiB, ~20min
2: ~14GiB, ~20min
3: didn't test
4: ~12GiB, ~24min
5: ~11GiB, ~26min
6: ~11GiB, ~30min (default?)
...
9: ~11GiB, ~1hour