[rrd-users] couple of questions

Simon Hobson linux at thehobsons.co.uk
Wed Sep 8 22:42:31 CEST 2010

Ricardo Kleemann wrote:

>I'm not yet very familiar with rrdtool, but could I read out data 
>values for an arbitrary period between time1 and time2 and add up 
>the values to come up with accumulated?
>I was thinking of a page where I could choose the dates and then 
>have a graph drawn for those dates, including the accumulated values 
>as well.

That's another approach - export/dump the data from rrdtool and 
process it externally. You can't do that in rrdtool graph - AFAIK, 
you have to create a CDEF which is "value times span" and which 
covers <span> period of time, and then use a VDEF to show the average 
of that.

Form the docs :
>Note that currently only aggregation functions work in VDEF rpn 
>expressions. Patches to change this are welcome.

Simon Hobson

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