[rrd-users] Re: Custom CDEF for Sum is Missing

[Arnold Nipper]

On 06.07.2004 14:58 Yurek, Matt wrote:

> I'm trying to generate a graph of hits per day across an entire server
> cluster.  Three servers handle the traffic to this one site, and the
> hits per day per server are located in 3 RRDs.
> 
> When I generate the graph with the following command, if one server is
> missing data (i.e. it was down for a day for maintainance, etc), the
> entire day is left blank, even though 2 out of 3 RRDs have valid data.
> 

That's because the value returned to either r1, r2 or r3 is "nan". You
may add anything to "nan", it stays "nan". And that is what you get graphed.

Hence you have to get around "nan" values. The easiest is with IF. Look
at
http://people.ee.ethz.ch/~oetiker/webtools/rrdtool/tutorial/cdeftutorial.html
more to the end (search for "using a recently created RRD"),




Arnold

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