[rrd-users] Unexpected decimal values in RRA

Steve Shipway s.shipway at auckland.ac.nz
Mon Nov 3 21:55:20 CET 2008

> > > When I fetch the values I see this:
> > > 1225359000: 3.8814344466e+03 -7.3078100609e-05
> > > 1225360800: 3.8815660814e+03 7.3156179499e-05
> >
> > Data time window normalisation.
> >
> OK. I think I see. I have also "ignored" the importance of the start time
> of the RRD upon creation I guess.
> Those two samples above have the times 10:30:00 and 11:00:00, but I run
> the polling scripts at 10:10:00 and 10:40:00.
> Are my asumption correct ? That the start time is crucial and must be
> taken into account when you set the actual polling times ?

The RRD will always be created with 'buckets' aligned on the interval boundary; IE, if your interval=5min, then the buckets will be 10:00, 10:05, 10:10 etc no matter when you create it.  So the start time doesn't actually matter, the important things is the times you store the data against.  If you have the buckets at 10:00, 10:05 etc and store your data against 10:01 you will get data normalisation, if you store it against 10:00 you will not.


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