[mrtg] Re: Peaks Crush Graphs

[Jay Hennigan]

On Sat, 9 Oct 2004, Jim McAtee wrote:

> I'm monitoring bandwidth on a 10 Mbps circuit which typically runs well
> under 1 Mbps.  Every once in a while I'll get a very bad single data point
> spike up to 7 or 8 Mbps and this spike will just crush down the rest of
> the data being graphed.
>
> A. What's a good way to contain this?  ABSMAX?  Manual scaling?

That depends on what is causing the "bad single data points".  If it is
genuine traffic of short duration, then you need to ask whether you are
more interested in accurate data or pretty graphs.
>
> B. If I set ABSMAX and then delete all the graphs for a data set, would
> the newly generated graphs suppress the spikes or is it once the data
> point is in the database I'm SOL until I can either edit it out or it
> scrolls out of the data set.

I believe that it will suppress the spikes when MRTG recalculates the
graphs, 5 minutes , 30 minutes, 2 hours and daily.

Beware that doing this will give you nicer-looking graphs that don't
necessarily represent the reality of the parameters you're measuring,
which can be a bad thing.

There may also be a de-spike utility in the contrib directory, I seem to
recall such.

--
Jay Hennigan - CCIE #7880 - Network Administration - jay at west.net
WestNet:  Connecting you to the planet.  805 884-6323      WB6RDV
NetLojix Communications, Inc.  -  http://www.netlojix.com/

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