[rrd-users] Numbers

Simon Hobson linux at thehobsons.co.uk
Sun Jan 4 08:39:45 CET 2009

Paul Halliday wrote:

>I will begin by saying my math is terrible - this might be right.
>Here is two runs:
>what I put in:
>4297607 || 3460967
>What I get:
>4.0777821933e+06 || 3.3850085800e+06
>Is this right?
>my rrd declarations look like:
>rrdtool create $rrd_dir/in_out_in_test.rrd --start `date -v0H -v0M
>-v0S "+%s"` DS:in_out_in:GAUGE:600:U:U RRA:LAST:0.5:1:105120
>rrdtool create $rrd_dir/in_out_out_test.rrd --start `date -v0H -v0M
>-v0S "+%s"` DS:in_out_out:GAUGE:600:U:U RRA:LAST:0.5:1:105120
>I have tried absolute .. average as well and I get the same numbers.

There isn't enough information there to be sure, but I'll guess that 
the timestamp of your updates is not on a step boundary (ie an 
integer multiple of step since unix epoch). If your updates are not 
exactly on a step boundary, then rrd will normalise the values - it 
adjusts the figures to fit the fixed 'bins' it has to put the data 

Alex has some excellent descriptions of this on his website :

Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
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