[rrd-users] Simple questions about RRD

Jean-Yves Avenard jyavenard at gmail.com
Sat Dec 5 14:01:53 CET 2009


2009/12/5 A Darren Dunham <ddunham at taos.com>:
> You can change the RRA's consolidation function at the top easily to see
> how if it were AVERAGE already, there's no differences between the
> second two graphs.
> Hopefully that demonstrates the differences pretty well.

It does ... thank you for enlighting me

As I was thinking more into yesterday ; I too had felt that for
AVERAGE is result would be quite obvious ; but for the MIN and MAX
some issues would arise...

Now I have an extra question on how the RRA/consolidation works...

Say I store 5 years of 5 minutes average ; is there any points of also
storing 5 years of 30 minutes average, 5 years of 2 hours average etc?

I would have assumed that it wouldn't matter ; except when retrieving
the 30 minutes/2 hours average extra processing is required as it
needs to retrieve more values.

Now; if I use reduce=AVERAGE for all my graph like
DEF:total=currentcost.rrd:total:AVERAGE DEF:ch2=currentcost.rrd:ch2:AVERAGE \
DEF:solar=solarprod.rrd:total:AVERAGE DEF:ch1=currentcost.rrd:ch1:AVERAGE \
DEF:ch2min=currentcost.rrd:ch2:MIN:reduce=AVERAGE \
DEF:ch1min=currentcost.rrd:ch1:MIN:reduce=AVERAGE \
DEF:ch2max=currentcost.rrd:ch2:MAX:reduce=AVERAGE \
DEF:ch1max=currentcost.rrd:ch1:MAX:reduce=AVERAGE \

Do I even need to create the RRD with MIN and MAX ? or it can be all
done from the AVERAGE RRD database ?
In my case, I create the RRD with:
100 day of 1 minute average
5 years of 5 minutes average

rrdtool create currentcost.rrd -s 60 \
DS:total:GAUGE:300:0:U \
DS:ch1:GAUGE:300:0:U \
DS:ch2:GAUGE:300:0:U \
DS:ch3:GAUGE:300:0:U \
RRA:AVERAGE:0.5:1:144000 \
RRA:AVERAGE:0.5:5:525600 \
RRA:MIN:0.5:1:144000 \
RRA:MIN:0.5:5:525600 \
RRA:MAX:0.5:1:144000 \

Not creating a MIN and MAX one would reduce considerably the size rrd file.

Here is my result so far ... You can click on parts of the graph to
automatically zoom-in for extra details.


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