[rrd-users] Maximum number of data sources/max cdef size.

Martin Sperl rrdtool at martin.sperl.org
Sat Feb 10 13:23:09 CET 2007


I remember submitting a patch to Tobi that defines a CDEF called AVG, 
that does ignore NULL values.
I now did check if this is in the SVN branch and I can confirm this is 
Maybe this is what you can use...


P.s: I remember having used a very complex CDEF to work around this for 
just 4 values and the patch to rrdtool was much shorter ;)

Simon Hobson wrote:
> George Barnett wrote:
>> I'm aggregating boxes into a graph to draw a cluster and I'm getting
>> null values.
>> Is there a maximum number of datasources in 1 graph?
>> Is there a maximum size of a cdef?
>> I've found that if I do this with only a few DS's, it works fine.  Maybe
>> somebody has tried this before?
> <snip>
>> "CDEF:gclient_requests=1aggavgclient_requests,2aggavgclient_requests,+,3aggavgclient_requests,+,4aggavgclient_requests,+,5aggavgclient_requests,+,6aggavgclient_requests,+,7aggavgclient_requests,+,8aggavgclient_requests,+,9aggavgclient_requests,+,10aggavgclient_requests,+,11aggavgclient_requests,+,12aggavgclient_requests,+,13aggavgclient_requests,+,14aggavgclient_requests,+,15aggavgclient_requests,+,16aggavgclient_requests,+,17aggavgclient_requests,+"\
> Are you aware that if ANY of the values is unknown them the result is 
> unknown ? So for example, if you were not collecting samples for one 
> system for a while, then you would have a gap in the graph.
> You have to do a test for unknown values and replace them with zeros 
> before adding them all together. Have a look back through the 
> archives, it's come up before.
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