[rrd-users] rrdtool - features ... 2nd y-axis

Tobias Oetiker tobi at oetiker.ch
Sat May 31 11:21:37 CEST 2008


> I guess this is a special question for Tobias, however, any answer welcome.
> I've searched the archives for features like a second y-axis and I found
> that people have started working on this many years ago ...
> Is there any particular reason it never made it into the released code?

there was never a generic patch with a sensible interface. If you
are interested in the second axis thing, please, before you start
coding, come up with a configuration method and discuss it on the
developers list ...

> I also found that the values in rrd seem to be stored as double float,
> using 8 bytes each - however, using 64bit integer values would be more
> precise (in terms of reproducable) and still enough for +/- 1e+19 ...
> Counting bytes that would mean ~10 Exabytes ...
> For some of my projects I would prefer having integer values, especially
> if you use the rrd not only for grahing, but for logging as well.
> Are there any attempts in that direction?

Since rrdtool does automatic resampling of data as it comes in,
using integers for data storage does not seem to be a good idea.
OTOH, if you use a counter type data source, rrdtool uses integer
math to calculate the difference between two consecutive counter
readings ...

> If I'm going to try to implement that change myself - as the
> author of that tool, Tobias, how would estimate the amount of
> time needed? I guess it will only affect the database part of it
> - not the graphing?

the integer change? well as I said, this would cause all sorts of
precision problems due to the resampling and as such does not
strike me as a very rewarding venture ...

what is it that you try to achieve ? with integers for data storage


> This is not meant to be any critism - the rrdtool is great as it is!
> Many thanks for your feedback.
> Rgds.
> - Karl
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Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten
http://it.oetiker.ch tobi at oetiker.ch ++41 62 213 9902

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