[rrd-users] Re: Interpreting RRD output - Maximum

Lyle Brooks brooks at deseret.com
Wed Apr 10 23:54:31 MEST 2002

Quoting Alex van den Bogaerdt (alex at slot.hollandcasino.nl):
> Lyle Brooks wrote:
> > I'm getting acquainted with RRDtool and have started to do
> > some data collection and graphing.  In doing so, I've come 
> > across some areas where I'm not understanding the results.
> > Inititively, I would think that "maximum" on the 5 day graph would
> > include this "maximum" found on the 24hour graph.
> You need to brush up on consolidation.


> You are consolidating averages.  The average of (1,2,3,4,5) is 3.
> max(1,2,3,4,5) is 5 while max(avg(1,2,3,4,5)) is 3.

Ok, That I follow.  I guess I'm not understanding what the proper
incantations are to make RRDTool do that.

Is there a text on "basic consolidation" I could review?

> You need more RRAs.  They should keep the maxima.  When you're
> going to plot and/or print maxima, use those RRAs.

I thought I was doing that, since I have RRAs defined for 


      'RRA:AVERAGE:0.5:1:600',    # Every 5 minutes, keep 50 hours
      'RRA:AVERAGE:0.5:6:600',    # Every 30 minutes, keep 300 hours (12.5 days)
      'RRA:AVERAGE:0.5:24:600',   # Every 2 hours, keep 1200 hours (50 days)
      'RRA:AVERAGE:0.5:288:732',  # Every day, 732 days (approx. 2 years)




I defined these thinking that RRDTool would keep consolidation functions
(AVERAGE,MIN,MAX,LAST) for each DS I define.

Similarly, I must be doing something wrong because all these commands
generate the same output, which is not what I anticipated.

rrdtool fetch myfile.rrd AVERAGE -s -24hr
rrdtool fetch myfile.rrd MIN -s -24hr
rrdtool fetch myfile.rrd MAX -s -24hr
rrdtool fetch myfile.rrd LAST -s -24hr

At first I thought that my error was on the output side (ie. when I 
generated the graph), but when I fetch the data and get the same output
regardless of the consolidation function, I think the error must be
on the input side.

I've read the tutorials, and the man pages and looked through some 
sample code, but I've clearly missed something important.

Thanks for any help.

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