[rrd-users] Re: Graphing other resolutions....

Alex van den Bogaerdt alex at slot.hollandcasino.nl
Fri Jun 22 12:52:38 MEST 2001

Hamish Whittal wrote:

> Ok, I did some reading of what Alex said to spamfilter about the graph
> getting the 'best' resolution of data. I have managed to figure out most
> of what he had to say, but I still don't understand the pixels thing. I
> seem to get a stepped graph. This is not what I want, as it looks like
> data points are plotted 'between' by real data points. Perhaps someone
> would be kind enough to explain the finer points of the pixels in the
> grapher.

I think the best way to explain this is:

RRDtool is not graphing points.  RRDtool is graphing intervals.

By the way, RRDtool isn't storing values on a certain time, RRDtool
is storing rates over an interval.

A plotted interval simply must be a whole number of pixels.  If the
interval size is large with respect to the total graph time, each
interval will be plotted on more than one pixel.

Example: your graph is 400 pixels wide.  You are plotting a certain
DS starting from 12:00 today until 13:00 today.  This is 3600 seconds.
If each interval is 90 seconds, RRDtool will plot 40 intervals and
each interval will be shown on 10 pixels.

Does this help?

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