[rrd-users] Things not adding up

[Tobias Oetiker]

Hi Jared,

Today Jared Watkins wrote:

> I'm working on my first custom rrd project and I'm having an issue with
> things not adding up correctly in a stacked graph.
>
> http://farm6.static.flickr.com/5105/5592424900_9a13016d57_b.jpg
>
> I'm most interested in the max values for this data and if you add up all
> the individual max values you get a value that's 120.15 greater than the
> total printed on the graph both visually and in the gprints.   Here is
> another example using only 2 samples:
>
> http://farm6.static.flickr.com/5095/5591833819_9a5942d74a_b.jpg
>
> And the relevant code?
>
>     RRDs::graph "$img/combined-$interval->{label}.png",
>         "$interval->{period}", "$interval->{end}",
>         "-t DSL Aggerate - $interval->{label}",
>         "-h", "$interval->{rezH}", "-w", "$interval->{rezW}",
>         "-l 0",
>         "-a", "PNG",
>         "-v bits/sec",
>         "-b", "1000",
>         "DEF:er01agas1in=$rrd_dir/er01.yul01.30004.rrd:in:MAX",
>         "DEF:er01agas1out=$rrd_dir/er01.yul01.30004.rrd:out:MAX",
>         "DEF:er01agas2in=$rrd_dir/er01.yul01.1418299.rrd:in:MAX",
>         "DEF:er01agas2out=$rrd_dir/er01.yul01.1418299.rrd:out:MAX",
>         "DEF:er01agas3in=$rrd_dir/er01.yul01.1385232.rrd:in:MAX",
>         "DEF:er01agas3out=$rrd_dir/er01.yul01.1385232.rrd:out:MAX",
>         "DEF:er01agas4in=$rrd_dir/er01.yul01.1819030.rrd:in:MAX",
>         "DEF:er01agas4out=$rrd_dir/er01.yul01.1819030.rrd:out:MAX",
>         "DEF:er02agas1in=$rrd_dir/er02.yul01.6.rrd:in:MAX",
>         "DEF:er02agas1out=$rrd_dir/er02.yul01.6.rrd:out:MAX",
>
>
> "CDEF:totalin=er01agas1in,er01agas2in,er01agas3in,er01agas4in,er02agas1in,+,
> +,+,+",
>
>
> "CDEF:totalout=er01agas1out,er01agas2out,er01agas3out,er01agas4out,er02agas1
> out,+,+,+,+",
>
>         "LINE1:totalout#000000:Total Out     ",
>         "GPRINT:totalout:MAX: Max\\: %5.2lf %S",
>         "GPRINT:totalout:AVERAGE: Avg\\: %5.2lf %S",
>         "GPRINT:totalout:LAST: Current\\: %5.2lf %Sbits/sec\\n",
>
> The data is being collected every 60 seconds and the rras are setup to keep
> 7 days worth of 1 minute samples and 3 years worth of daily max values for
> long term peak trending.   I can't find any reason these shouldn't be adding
> up.. and I'm at a loss as to how to fix it.

within the chart, the data gets pre-consolidated to the pixel
resolution of the graph, so if one pixel is 2 minutes wide, the
incoming max values will be consolidated into one slot using the
same consolidation function used on the original data ...

when you then add these pre consolidated max values the result will
be larger the total ...


cheers
tobi

>
> Thanks,
> Jared
>
>
>
>

-- 
Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland
http://it.oetiker.ch tobi at oetiker.ch ++41 62 775 9902 / sb: -9900