[rrd-users] newbie rrd question - probably a very old issue

Dan Gahlinger dgahling at hotmail.com
Sat Sep 1 17:59:12 CEST 2007

what about the command-line query function?
there is no "space limitation" with that.

why is that consolidating?

and I still disagree with the analysis.
even as you say, it has to shrink it to fit, that doesn't mean it should be 
averaging out the maximum (or the minimum) and adjusting the graph.

you say there isn't enough space, I disagree. take a look at a "Nasdaq" 
graph for comparison.
whether you do a day, week, month, 6 months, or a year, the graph is the 
same size with the same amount of available space, yet it shows every 
minimum, and every maximum correctly. it never averages those out. and all 
on one graph.

I'll post a link to some examples if you would like to compare - not sure it 
can relate directly though.

the point is, it is possible to do, so rrd should also be doing this. but 
even more to the point,
the command-line tools are consolidating - and those have infinite space, so 
they definitely should not be consolidating.

can you explain why the command line tool is doing the same thing? I'd 
really like an explanation for that.


>From: "Marc Powell" <marc at ena.com>
>To: <rrd-users at lists.oetiker.ch>
>Subject: Re: [rrd-users] newbie rrd question - probably a very old issue
>Date: Sat, 1 Sep 2007 10:36:20 -0500
> > -----Original Message-----
> > From: rrd-users-bounces at lists.oetiker.ch [mailto:rrd-users-
> > bounces at lists.oetiker.ch] On Behalf Of Dan Gahlinger
> > Sent: Saturday, September 01, 2007 9:31 AM
> > To: alex at ergens.op.het.net; rrd-users at lists.oetiker.ch
> > Subject: Re: [rrd-users] newbie rrd question - probably a very old
> >
> >
> > in our case, we only had 2 days worth of data, actually less than 1000
> > bits
> > of data.
> > so on the weekly graph there are enough points.
> >
> > on the graph we can clearly see the "90" spike on the daily graph, but
> > weekly graph, that days spike has been changed to "30" and is plotted
> > 30.
> > this is very bad. it shouldn't happen.
>Look at it this way. Assuming 5 minute samples, there are 288 data
>points in 1 day. On a 300 pixel wide graph, you have enough space to
>graph each single data point and then some. Now you ask rrdtool to graph
>a weeks worth of data points in a 300 pixel wide graph. There are 2016
>possible data points from which it must choose only 300 to display. How
>should it do this? RRDTool uses the best fitting RRA and the
>consolidation function you specify (likely AVERAGE).
>The fact that you only have two days of data doesn't mean RRDTool is
>going to change the way it creates a weekly graph. You've told it to
>graph a weeks worth of data so it'll do the best it can to show you a
>weeks worth of data, NAN or not. You only had two days worth of data but
>still asked rrdtool to show 7 days worth. It will, properly, consolidate
>what you have to fit the two days and show 5 days worth of NAN data.
>rrd-users mailing list
>rrd-users at lists.oetiker.ch

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