[rrd-users] Re: Totalling (finish, puh)

Tobias Oetiker oetiker at ee.ethz.ch
Fri May 17 15:48:43 MEST 2002

Today Matthias Mikuletz wrote:

> But then there is a need for different CDEF's (or a totalling function, or
> a variable that can be used in a CDEF) in one 'rrdtool graph' command.
> Because for adequate totalling you need distinct multiplications for the
> different RRA's.

no you do not ... all the RRAs store the same kind of data ... this
is totally transparent ... the only difference is the resolution

> > Sure, but this is only presentation ... the internal data format
> > is irrelevant as long as it is consistant ... you can draw graphs
> > 'per whatever unit of time you want' this is very simple ....
> Yes. I agree. It's much more consistent to have the same type of date
> (rate based on the same interval) in all of the RRA's of one RRD.
> But see above. In 1.0 I can only use the same set of CDEF's for all of the
> RRA's in an RRD (am I wrong?) in one call of 'rrdtool graph'. This way I
> cannot multiply the rate in one RRA to get 'per hour' while multiplying
> the rate in the other RRA to get 'per day'.

forget the RRAs, this are totally irrelevant when graphing ...
rrdtool takes care of selecting one which has data available
necessary for the graph ... The reason RRAs exist is that you need
to have a way to tailor the data storage structure of the RRD file
... how much data to keep at what resolution. rrdtool graph will
pick the RRA which holds the data which best matches the
requirements of the graph at hand


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