What is consuming my disc resource?

I just was noticed that my disk was almos empty, I deleted all saved snapshots but did not help.
How can I find what is eating my disk space?
I am very nervous that my system will crash very soon so please advice
Thanks a lot in advance!
It is a plain HA installation on a Intel NUC

As said deleted all snapshots in local media (many) and rebooted HA and that did not help.
I rebooted the server (the NUC) and now it’s back to normal.
No clue why but it helped…