[rrd-users] TOTAL consolidation function

Peter Amstutz tetron at ashura.umassp.edu
Mon Jun 25 22:59:22 MEST 2001


I'm trying to use MRTG to monitor errors (CRC, dropped packets etc) on
router interfaces.  I've already submitted a large MRTG patch to Tobias
which lets us have more than two data sets on a single graph using RRD as
our backend; now we're in the process of tweaking RRD's output so our data
is meaningful (and visible) and have come across a few issues with

The first is the inability to graph decimals between 0..1 when using a
logrithmic scale.  Now, when an error occurs we want to be able to see
both huge spikes and small bumps on the graph, so logorithms are the way
to go.  However, very small events (like a couple dropped packets) end up
being reduced into small decimals by MRTG (which incorrectly assumes it is
a rate, but that's another issue) and are not graphed because RRD doesn't
understand negative logorithms when graphing.

The second problem is that we're trying to graph changes in descrete
values, but we're not concerned with the actual rates.  For this, the
"total" consolidation function makes the most sense, since we would like
to know the actual total number of errors that occured.  However, I
gathered from the mailing list archives this feature was removed some time
ago.  Why was this done, and are there any patches floating around that
might re-add the feature?

Oh, I should mention that the man page for rrdtool still mentions that
"total"  is an available cosolidation function.

- Peter Amstutz

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