My db server (one cpu VM) is monitored by Nagios.

I've no experience with Nagios and I've trouble understanding this graph:

  • what is the unit on vertical axis?
  • and the averages? what is "m"?



The vertical axis is a dimensionless number indicating the average usage of the computer (more precisely, the numbers of processes waiting for CPU time, the so called load) in the last one, five and 15 minutes. My guess is that the "Average" is a separate average calculated by RRDtool (the utilitiy that creates this graph) over the values drawn in the graph and is in itself pretty meaningless. The m unit is likely just an indication that it uses "milli-units", so 1000m would represent a load of 1, and if e.g. the load1 would be constantly 1 over the graph, the Average would be 1000.

  • I doubt the averages aren calculated by RRDtool, nor by the script/process that's calling it. They are most likely based on the system averages which are the normal past 1, 5, and 15 minutes averages the system reports.
    – Gene
    Oct 8 '14 at 18:47
  • 1
    Nagios won't be taking averages, it only reports on the data there-and-then. RRDTool is reporting the averages here. It's also able to report the min and max as well if the command that generates the graph image requests it.
    – dannosaur
    Oct 8 '14 at 18:49
  • @Gene: You are most likely wrong. This is a value RRDtool can create over its data, like it can do other calculations as well. The system averages over 1, 5 and 15 minutes are plotted in the graph.
    – Sven
    Oct 8 '14 at 18:52
  • The "Average: 227.88m" in the legend is put there, and calculated, by RRDtool, as several people have already said.
    – Keith
    Oct 8 '14 at 19:05
  • @SvW thank you for the reference to the load article, I understand indeed that the load is actually the Exponential moving average of the number of processes using or waiting CPU time... About RRDTool, it's probably true, it's written on the right side of the graph...
    – Glasnhost
    Oct 8 '14 at 21:08

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