# [rrd-users] MAXIMUM consolidation over the sum of two counters

Dick van der Sijs saosijs at gmail.com
Tue Aug 27 18:27:27 CEST 2013

```Thanks for the confirmation! The sentence
Instead you will need to find max( max(counter1),max(counter2) )
(http://www.vandenbogaerdt.nl/rrdtool/min-avg-max.php) confused me a bit.
It's not what I need or want ;-)
So what I probably will do is use xport to calculate the sum with high
granularity (maxrows skyhigh), and then with some scripting (I usually use
perl for that) extract the data and populate a new rrd with the sum.

Like you I'm still pondering on how to deal with unknown data. In my case I
have 7 systems and if one of them has a period with unknown values, it
still can mean several things:
- it still carried traffic, but it did not end up in the rrd (e.g. simple
temp connection problem)
- it really was down and the other 6 systems carried all the traffic
So do I use + or ADDNAN for the total sum? Either choice can give "wrong"
resulting graphs. Without having knowledge about why some data is unknown there
is no way to correctly interpret these total sum graphs. In my particular
systems contributed to the total sum. Or maybe I can do a trick like AREA
graphing both the ADDNAN sum and the + sum on top of each other. I need to
in the graphs.

On Tue, Aug 27, 2013 at 5:37 AM, Simon Hobson <linux at thehobsons.co.uk>wrote:

> Dick van der Sijs wrote:
> > However, the way I understand that rrdtool works is that with rrdgraph I
> cannot get max(counter1+counter2).
> > That is, not unless I set up a third counter from the start in which I
> put the sum counter1+counter2.
> > The question is then if it is possible with rrdgraph alone, so without
> that third counter that I mentioned?
> > Note that I am not looking for max( max(counter1),max(counter2) ), but
> really for max(counter1+counter2).
>
> applied any consoilidation because the values you want simply do not exist.
>
> To get max( counter1 + counter2 ) then you **MUST** store
> counter1+counter2 prior to applying consolidation.
>
> I have a couple of things I'd like to do which have the same problem. Only
> I haven't yet figured out the best way to reliably and simply fetch values
> from multiple remote systems (and allowing for the possibility of one or
> more being down) so I can store the sum of the values.
>
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