[rrd-users] generating charts from multiples RRA

Alex van den Bogaerdt alex at vandenbogaerdt.nl
Thu Sep 10 08:01:19 CEST 2015

> That seems to be simple, but how do I specify to use the last two RRAa,
> which have an average and max (respective) for a whole day items checked?

The difference between the two RRAs *is* the consolidation function ...

> Ignoring the consolidation function (AVERAGE or MAX) specified in the
> graph command,

... so you should not ignore that. Specifying a consolidation function
makes a big the difference in the RRA selection process.

> how do I make sure I'm fetching from the correct RRA? Only
> by using "--start" or "--end", or do I have also to specify the step 
> (24)?

RRDtool tries (and mostly succeeds) to select the 'correct' RRA for the
purpose. RRDtool will try hard to find the best match.

In your case, your database has only one RRA with MAX data, so asking for
MAX will always select that RRA. There is no choice.

Only in the case of AVERAGE there is a choice to make. If you query for
more than 28x4 hours, the bigger RRA (90 rows of 1 day each) should be
I don't mean '... you should select...', I mean '... RRDtool should ...'


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