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[Quenten Grasso <QGrasso@xxxxxxxxxx>]

Hi Everyone,

I'm currently using collectd with graphite collecting some network interface stats, using the "if_octets" data type in collect D, which is explained here

http://collectd.org/wiki/index.php/Data_source
DERIVE
These data sources assume that the change of the value is interesting, i.e. the derivative. Such data sources are very common with events that can be counted, for example the number of emails that have been received by an MTA since it was started. The total number of emails is not interesting, but the change since the value has been read the last time. The value is therefore converted to a rate using the following formula (see: Finite difference (Wikipedia)<http://en.wikipedia.org/wiki/Finite_difference>):
[\textit{rate} = \frac{\textit{value}_\mathrm{new} - \textit{value}_\mathrm{old}}{\textit{time}_\mathrm{new} - \textit{time}_\mathrm{old}}]
Please note that if valuenew < valueold, the resulting rate will be negative. If you set the minimum value to zero, such data points will be discarded. Using DERIVE data sources and a minimum value of zero is recommended for counters that rarely overflow, i.e. wrap-around after their maximum value has been reached. This data source type is available since version 4.8<http://collectd.org/wiki/index.php/Version_4.8>.


This then sends it to whisper and stores it every 2 seconds and all of this seems to be working..

However when i pull the data out of graphite the graphs are completely off I've tried using the nonNegativeDerivative() function which makes the data look closer to what it should however its like the scale it way off, I was suggested to use a scale of 0.125 however this isn't close, however a scale of 4 is closer but still not accurate I'm not sure what's going on here..

Has anyone else attempted this previously with success?

Thanks,
Quenten