[rrd-users] HELP I dont understand RRA's

Simon Hobson linux at thehobsons.co.uk
Tue Jan 26 12:20:08 CET 2010

tony at specialistdevelopment.com wrote:

>So in a last ditch effort to "get" it here is my example with my 
>workings, can you guys take a look and see im sort of on the right 
>So i want to graph my network traffic. i want to read the data every 
>minute so my step is 60 seconds, also wait 120 seconds before unknown.
>RRA 1 - 60 PDP's, so every minute, then create 1 CDP for an hours info.
>RRA 2 - 60 PDP's make 24 CDP's for a days info.
>RRA 3 - 1440 PDP's make 31 CDP's for a months info.
>rrdtool create network.rrd \
>    --start N \
>    --step 60 \
>    DS:bytesIn:DERIVE:120:U:U \
>    DS:bytesOut:DERIVE:120:U:U \
>    RRA:AVERAGE:0.5:60:60 \
>    RRA:AVERAGE:0.5:60:24 \
>    RRA:AVERAGE:0.5:1440:31
>Or have i got my numbers totally wrong?

If I understand you correctly, you want to keep one minute samples 
for an hour, one hour periods for a day, and 31 periods for a month. 
If that is the case, then you've got one error there, your first RRA 
should have 1 PDP per CDP.

rrdtool create network.rrd \
    --start N \
    --step 60 \
    DS:bytesIn:DERIVE:120:U:U \
    DS:bytesOut:DERIVE:120:U:U \
    RRA:AVERAGE:0.5:1:60 \
    RRA:AVERAGE:0.5:60:24 \

Simon Hobson

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