[rrd-users] One-off and no-data-problem

Alex van den Bogaerdt alex at vandenbogaerdt.nl
Thu Dec 30 12:59:42 CET 2010

> It was, but it's not enough for rrd tool to calculate a value for the
> whole period.It knows that at time 400 the value was 123. Before that
> it has to assume the values are unknown as you've not supplied any
> earlier updates.

To avoid confusion: assuming values are unknown before 300000400 is wrong.
 After all, rrdtool updates are done at the end of an interval, not at the

at time xyz your counter value is x
at time xyz+300 your counter value is x+y
rrdtool computes the rate at time xyz+300. The resulting rate is valid
between times xyz and xyz+300.
After this, normalization is done to make a PDP, and consolidation to get
a CDP.

GAUGE is no different. The only difference at this stage is that it needs
not do (x+y)-x and (xyz+300-xyz). The "resulting rate" (the number being
fed to RRDtool) is still valid bewteen xyz and xyz+300.

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