disk space consumption monitor documentation query

Where is the disk space consumption monitor documented?

I've recently started getting messages telling me the monitor has gone down. I can verify that VM reports it as down, starting it with the GUI doesn't work. I can delete the monitor and reinstall it then it comes up working after a short delay but then goes down again.

The similarly named disk space monitor is fine. There is about 50 GB free on the volume, about half. I'm not concerned about disk space per se, just the monitor.

Will RTFM if I can find it.

Dave