[rrd-users] Re: Wrong data in rrd file

[Synox]

>real data in rrd file are:
>
>1120199400: 3.0000000000e+00
>1120200000: 2.5163305117e+00
>1120200600: 2.4773337700e+00
>1120201200: 2.5148369450e+00
>1120201800: 3.4426964500e+00
>1120202400: 3.5409875000e+00


From:
http://people.ee.ethz.ch/~oetiker/webtools/rrdtool/tut/rrdtutorial.en.html

(...) One important feature of RRDtool has not been explained yet: it is
virtually impossible to collect data and feed it into RRDtool on exact
intervals. RRDtool therefore interpolates the data, so they are stored
on exact intervals. If you do not know what this means or how it works,
then here's the help you seek:

Suppose a counter increases by exactly one for every second. You want to
measure it in 300 seconds intervals. You should retrieve values that are
exactly 300 apart. However, due to various circumstances you are a few
seconds late and the interval is 303. The delta will also be 303 in that
case. Obviously, RRDtool should not put 303 in the database and make you
believe that the counter increased by 303 in 300 seconds. This is where
RRDtool interpolates: it alters the 303 value as if it would have been
stored earlier and it will be 300 in 300 seconds. Next time you are at
exactly the right time. This means that the current interval is 297
seconds and also the counter increased by 297. Again, RRDtool
interpolates and stores 300 as it should be.


I think this is the problem ;)

greez synox

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