[rrd-users] RRDtool computing logic help

aleluya huangyongjian at gridsum.com
Thu Apr 3 17:12:26 CEST 2014

Hi, everyone,

I am learning RRDtool, I can't find any documents that describe what would
happen when multiple sampling points were inserted in a single step.

Here's my test:

rrdtool create mydata6.rrd --start 1396419600 --step 4
DS:mem:GAUGE:2000:0:4000000 RRA:AVERAGE:0.5:1:50

rrdtool updatev mydata6.rrd 1396419601:8 1396419604:14

I got the output:
return_value = 0
[1396419604]RRA[AVERAGE][1]DS[mem] = 1.2500000000e+001

In the example above, the step is 4 seconds, I insert two sampling points
whose value are 8 and 14 respectively, why I got the CDP value 12.5?

What's the internal logic? 
Are there any documents describing the computing logic of rrdtool in more

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