Help! Computation possible on Graph?

[ethorn]

I want to take the RRD created using Generic HDD graph that comes with Cacti and add a line that states percentage used. Currently the graph show used and total. I want to add a line that shows percent used. Is there a way to do this like the sumation or 95th percentile for bandwidth usage?

[pestilence]

Check the manual page of rrd for cdefs, through them you can do as many math calculations as you want.