[rrd-users] Re: numbers in the db are different from the actual ones??

Alex van den Bogaerdt alex at slot.hollandcasino.nl
Wed Nov 28 21:30:12 MET 2001

Tekin Gulsen wrote:

> I'm lost in a strange problem. I'm sure I missing something. The problem is
> that the values in the database do not match the actual increments.

That's right.  You are not working with increments, you are working
with rates.

The calculation is not (new-old), it is ( (new-old) / (time_new-time_old) )
this is also referred to as delta(value) divided by delta(time).

The time component is always there, even for a GAUGE.  

counter:  rrdtool calculates both delta(value) and delta(time).
derive:   dito, however the rate can be negative
absolute: you are feeding delta(value), rrdtool computes delta(time)
gauge:    rrdtool doesn't calculate delta(value) nor delta(time)

The resulting rate (after calculations, if necessary) is subject to
normalization (explained further on faq.mrtg.org and in the docs).

If you want to know delta(value) this means that you have to multiply
by delta(time).  This is because ( (X / t) * t ) results in X.  This
may give you slightly different numbers than those you put in, this is
because of the normalization.

 / alex at slot.hollandcasino.nl                  alex at ergens.op.het.net \
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