[rrd-users] Re: Graph data is affected by the size of PNG image

[Alejandro Galue]

Hello Dan,

Thanks again.

So, in order to use reduce=MAX, the RRD must have an RRA with cf=MAX (Am 
I right?)

But, the RRA that I'm using use maximun resolution (pdp_per_row=1), and 
contain 4 months of data using 300 sec. sample step; so an RRA with 
CF=MAX for this resolution will be the same as CF=AVERAGE or any other 
CF because use only one sample.

Do I must duplicate the information creating two RRAs for max-resolution 
in order to avoid this problem ? (i.e. duplicate rrd file size?)

Please correct me if I'm wrong.

Best regards,
Alejandro Galue.

Dan Cech wrote:
> Alejandro Galue wrote:
>> Hello Dan,
>>
>> Thanks for your quick response. I really appretiate that.
>>
>> I included an attach with two files inside:
>>
>> the RRD called  379.framerelay1.rrd
>> a perl script called graph.pl
>>
>> This file generate the graphs for the tests.
>>
>> The small graph use (500x150) and the big graph use (800x300)
> 
> After looking through your attachment, I see that you are indeed using a
> DS defined with AVERAGE, then attempting reduce=MAX.  This is definitely
> part of your problem, and will never give you consistent results.
> 
> You should be consolidating the data using an RRA for each of the types
> of data you wish to extract, so in your case you'd want and RRA for
> MIN,MAX,AVERAGE and LAST for each DS at each resolution.  Then you can
> use the correctly aggregated data to get accurate figures out.
> 
> Right now, your data is first averaged when going into the RRA, then
> reduced with MAX, then aggregated in your graph.  So you end up with the
> maximum of the maximum of the average, the average of the maximum of the
> average, etc.
> 
>> I used "step=300:reduce=MAX" and "step=300" alone with no success, but
>> the graphs is a little bit better than with or widthout "reduce=MAX".
> 
> By fixing the step size, you're reducing the change between the 2
> graphs, by forcing them to use the same RRA, but your figures will still
> be incorrect.
> 
>> reduce=MAX is used for pixel reduction technique and is not related to
>> consolidation function used to fetch data; am I right ?
>> Is this a Bug ?
> 
> See above, your data is not being consolidated in a way that would allow
> rrdtool to answer the question you are asking.
> 
> Dan
> 
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