Alert rule - diff between two graphs


I’ve got two queries in one graph.

  • Allocated storage in GB
  • Used storage in GB

I would like to set an alert if the difference between the two drops below a certain threshold. I’m not able to find documentation to do this with the Alert Conditions. Same thing goes when I merge the two queries into one query and so I got two series.

Isn’t what I’m trying to do possible?

Never mind, I’ve created a third query which calculates free. Then the alert rule targets this query and monitors with the below threshold.