[rrd-users] RRD aggregating data into impossibly large numbers.

Gabriel Fortuna Gabriel.Fortuna at is.co.za
Wed Jun 13 17:04:52 CEST 2007

Hi all,

	I'm hoping someone can help me with this very strange problem
I'm having.

	I'm using rrd to store and graph data that we collect from a
number of modems connected to a satellite system. Every 5 minutes, I
query the satellite systems performance statistics database and input
those numbers into an rrd file per modem. So far so good. :) Next, we
have a little web interface where people can go and pull graphs for each
modem. This all works fine... until I decide to view weekly and or
monthly data.

	What seems to be happening is rrd is rolling up the primary data
points, but, something is completely messing up the aggregated data, and
storing it as impossibly high and impossibly low (for these modems at
least, not mathematically) numbers.

	I'll give you an example: I store an availability number which
is either 0 (unavailable) or 100 (available). In the monthly rra, the
values get aggregated to into numbers with exponents in the hundreds:

Snip from an rrdtool dump.
<!-- 2007-05-28 08:30:00 SAST / 1180333800 --> <row><v>
2.0341983732e-230 </v><v> -3.4449528818e-105 </v><v> -9.1197725638e+251

	Now, I know these numbers can never be negative, because they're
hardcoded to originally be either 0 or 100. In fact, nothing in my
system is a negative number. I also scrub the numbers prior to updating
the rrd to make sure they conform to these rules, yet, the data is still
broken as it gets aggregated.

	Has anyone on this list ever seen similar behavior? Can anyone
provide me with help or advice? Many many many thanks in advance!

P.S - I'm updating my rrd's with RRDTool::OO (the latest version - 0.19)
RRDTool is also the latest version, 1.2.23. OS is RHEL ES4.



Gabriel Fortuna
Internet Solutions


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