[rrd-users] how to draw correct graph on server rrdfiles when some of them have zero/null values?

Shaojie Liu liusoaring at gmail.com
Tue Jan 5 10:37:15 CET 2010

it turns out a bug in code led to this problem.

however the "IF.. UN" PRN patch indeed fix another problem caused
in-continous boring space(undef+*=undef) in curves.

thanks a bunch.

On Tue, Jan 5, 2010 at 5:01 PM, Jean-Yves Avenard <jyavenard at gmail.com>wrote:

> Hi
> 2010/1/5 George-lll <liusoaring at gmail.com>:
> > but if some rrd files have zero/null value(indicate some servers got no
> > traffic at that period), the charts combined curve drop to zero too.
> Are they zero or undefined ?
> They do not mean the same thing.
> The reason you are seeting what you're describing is because
> undefined + anything = undefined..
> If the traffic was 0, you should have added 0 to the RRD via rrdtool
> update ; According to your RRD definition, if you do not feed any data
> for 2 hours, then entry will be undefined for that period.
> >
> > wondering there is a data validation before rrdtool starting up, so
> someone
> > let me know hwo to avoid?
> What you could do in your CDEF is something like this:
> CDEF:x=val1,UN,0,val1,IF,val2,UN,0,val2,IF,+ etc..
> This will replace all unknown values with 0.
> Jean-Yves
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