[rrd-users] Input values normalization

Alex van den Bogaerdt alex at vandenbogaerdt.nl
Tue Feb 18 16:05:38 CET 2014

I'm with Simon on the validity of normalized input. If your device will 
never report fractions of a degree, then the input will almost always be 
"wrong" anyway, and certainly not more correct than what RRDtool eventually 

This said...

Setting step to one is a good first step.
Next try to NOT have an RRA where steps==step, and NOT with consolidation 
function average.

There is nothing wrong with, for instance, setting steps==3600 and CF==MAX 
to remember the highest temperature reported during an hour, and to have 
this as the RRA with finest granularity.

You could have two RRAs, one remembering MAX the other MIN, and then show 
the temperature range seen suring any hour (e.g. a red area for the max 
temperature seen, overlayed by a blue area for the minimum temperature 

Not sure if cacti can do this, that's for someone else to answer, but 
RRDtool can do it.


----- Original Message ----- 
From: "ENTRESSANGLE, ERIC (ERIC)" <eric.entressangle at alcatel-lucent.com>
To: <rrd-users at lists.oetiker.ch>
Sent: Tuesday, February 18, 2014 3:17 PM
Subject: [rrd-users] Input values normalization


I would like the feedback of experienced rrdtool/cacti users about the 
following point :
I think I understood that rrdtool works with rates (through counter, derive, 
absolute types), and that in this case, the "normalization" step can make 

But I'm more doubtful about the "normalization" for gauge type, for example 
when I graph a plain temperature, because it means that the temperature on 
my graph is never exactly the real input value, unless data source step and 
cacti's poller are perfectly synchronized, but it is impossible when there 
are a lot of counters to retrieve.

The solution I found is to set a data source step to 1 second to avoid 
normalization, but this produces big rrd files with a lot of redundant 

I did not find a satisfactory solution up to now, thanks for any hint.




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