[rrd-users] need help with a graph

Alex van den Bogaerdt alex at ergens.op.het.net
Thu Sep 25 15:47:44 CEST 2008

----- Original Message ----- 
From: "LÉVAI Dániel" <leva at ecentrum.hu>
To: <rrd-users at lists.oetiker.ch>
Sent: Thursday, September 25, 2008 3:09 PM
Subject: [rrd-users] need help with a graph

> Hi!
> I need some help with a simple graph. To be honest, I don't really
> understand rrdtool, but I'm trying... really. :)
> So, I have a working mrtg configuration, which gets data from an snmpd,
> and then creates an rrd file.The mrtg script runs every one minute.
> From this rrd file I want to create a graph.
> I'm doing this:
> /usr/local/bin/rrdtool graph cpu.png --imgformat PNG --end now --start
> now-259200s --width 1000 --title CPU DEF:ds0a=janos_cpu.rrd:ds0:AVERAGE
> LINE1:ds0a#0000FF
> After this I get this graph:
> http://leva.ecentrum.hu/cpu.png
> My problem with this graph is that it has low resolution (for me).

The problem will be that data is not available in a higher resolution.
You are asking for 259200 seconds, which is 72 hours.  Assuming a step
size of 600 seconds, this means 4320 steps. Perhaps you have only 600 of
them available?

rrdtool info janos_cpu.rrd should show what is available. Look at pdp per
row, amount of rows and step size.

> I get the data every one minute, but in the graph it only shows one unit
> per half an hour. Is it possible to make it show one unit per one
> minute, or at least smaller than half an hour?

First try changing "--start now-259200s" into "--start end-3600s".  Does
this provide better resolution?  If so, increase 3600 to, say 36000.

At a certain point you will notice the resolution changes. That's when
you are asking for more data than is available in high resolution.

You can alter the amount of rows to keep using rrdtool resize. Make sure to 


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