I manage a number of linux fileservers. These all run applications written from 0-10 years ago. As sometimes happens, a machine will come close to, or run out of disk space. Reasons include applications not rotating log files, a machine with 500GB of disk producing 150GB of new files every month that were not written to tape, databases gradually increasing in size, people doing silly things...generally a bit of chaos.
Anyway, when a machine unexpectedly goes from 50% to 100% full in a couple of hours, I figure out what broke (lots of "du") and delete files or contact someone. I also can look at cacti graphs to figure out what the machine's normal disk usage is (e.g. for /home).
Does anyone know of any tools that will give finer grained information on historial usage than a cacti/RRD graph? Like "/home/abc/xyz increased 50GB in the last day".