Caution: IANAStatistican!

Beside that, the reliability of the check heavenly depends on your data and matching frequency.

Example:
./check_graphite.r graphite.example.org stats.host123.disk_free 3 '<50,<20' '<100*90,<100*45'

This would alert:
- critical  if disk_free is currently below 20GB
- critical  if disk_free will be below 100GB in 45 days(*)
- warning   if disk_free will be below 100GB in 90 days(*)
- warning   if disk_free is currently below 50GB


This check is quite expensive, so make sure it's not killing your nagios server.


(*) actually, this means "in FREQUENCY * n" extrapolated datapoints.