[rrd-users] Re: RRDTool graphs: various questions

John Murdoch John.L.Murdoch at ed.ac.uk
Thu May 27 12:08:24 MEST 2004

Hi Alex,

On Thu, 27 May 2004 11:34:44 +0200 Alex van den Bogaerdt wrote:

> On Wed, May 26, 2004 at 09:53:47AM +0100, John Murdoch wrote:
> > 1) Does anyone have an RPN function that can change MIN/MAX averages, so that on close inspection, the graph plots only one point rather than draw a "bar chart" for the time period in question. To clarify, if I was to create and RRA where there is one MAX value per day, currently it would be a continous line for the day, then instantly drop off/shoot up to the next point for the next day. I'd like to have one point at 12 noon every day, so that the lines slope between points.
> If you want an one-hour granularity, do so in your RRA.  Update at
> noon local time, and you get what I think you ask.

This does seem logical... but my other, more granular data is in a 15 min (--step 900) RRD, so updating at noon-only is impossible if I stay with the same RRD. :( I am guessing this is the cause of why MIN/MAX points are represented as continuous lines for the whole day. Should I construct a seperate RRD to hold the noon-based data? (see below for my DS/RRD layout)

> > 2) Is it possible to plot two RRAs using the same consolidation function, but with differing steps/rows, on the same graph? I'd like to plot two RRA AVERAGEs of varying granularity on the same graph, but I can't seem to do this. 
> There's no problem whatsoever to do this AFAIK.

Hmmm... this is puzzling me (using RRDtool 1.0.47). I've tried plotting the two different AVERAGES, but rrdtool graph seems to just pick the most relevant to the timescale and plots that twice. Here's my RRD layout (every 15 mins for 3 years):
"DS:users:GAUGE:1700:0:U", "RRA:AVERAGE:0.5:1:105120", "RRA:AVERAGE:0.75:96:1095", "RRA:MIN:0.75:96:1095", "RRA:MAX:0.75:96:1095"

Perhaps I should set out a seperate RRD for MIN/MAX/AVERAGE values for a day? This seems more logical in my opinion, as it'll eliminate both of the above problems. However, if you can see some flaws in the design of my RRD or my approach to graphing, I'll be very grateful if you let me know. :)



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