[rrd-users] Consolidation function (CF) per data source (DS) instead of per archive (RRA)

Fredrik Kers fredrik.kers at absilion.com
Tue Mar 27 10:24:27 CEST 2012


I have used rrdtool for a while and has since the beginning been wondering
about why the consolidation function (CF) is set per archive (RRA) and not
per data source (DS). I have many times been in a situation where I want to
store related parameters in the same RRD but I want to have different
consolidation done on them.

An example could be a weather data logger. Every hour I get the
min/average/max temperature, amount of rain and the average wind direction
and speed. All parameters should use the average consolidation except for
the min/max temperature, where the storing the "average min" and "average
max" doesn't make much sense.

And while I'm at it... I'm missing a consolidation function here. I would
like to consolidate the amount of rain with a "SUM" function, since that is
what I'm actually measuring at the weather station. I have found a
workaround for this by using AVERAGE consolidation and multiplying with the
step size when graphing. It works but it feels like a bad hack.

I might be able to create a patch that adds a SUM consolidation function if
there is a chance it will be included in rrdtool, but I don't have a good
proposal how to solve the consolidation per data source yet. Maybe there is
a reason why different data sources can not have their own consolidation
function within the same archive that I don't see.

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