[rrd-users] Re: strange rrd entries

Tobias Oetiker oetiker at ee.ethz.ch
Sat Sep 16 00:04:50 MEST 2000

Yesterday you sent me mail regarding [rrd-users] strange rrd entries:

WCE> I just started using rrd, I am considering switching from mrtg.
WCE> I created an rrd database and fill the database with ifInOctets and
WCE> ifOutOctets, here is a sample of the strings I send to rrdtool update:

WCE> 969049133:30125822936:34199518912
WCE> 969049193:30231816104:192880048

WCE> When I do an rrdtool fetch I get the following:
WCE> 969049080 1576309.577778 3788594.884444
WCE> 969049140 1633104.217778 35868668970862180.000000
WCE> 969049200 1716222.053333 271577065029557248.000000
WCE> 969049260 1335635.388333 4775705.576111

octet counters normally wrap at 2^32-1 rrdtool knows this and when
a counter value gets smaller from one update to the next it assumes
that such a wrap has occured and calculates the difference taking
the wrap into account. In your case it was obviously not a wrap
which caused the counter to shrink. Rather a reset maybe. The way
for rrdtool to detect this is, that you tell it the range of
numbers you expect to see setting a min and max limit when creating
the RRD. You have obviously not done this, so rrdtool has no way of
figuring out what is going on when your counter shrinks ...


WCE> notice the huge numbers at times 969049140 and
WCE> 969049200, what causes these? How can I filter these
WCE> or avoid these? There is nothing in my input data
WCE> that should cause such spikes. Do I need to run the killspikes
WCE> routine?

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