[rrd-users] Normalization and NaN (?)

Derek Simkowiak ubuntu at realloc.net
Thu Dec 23 23:08:04 CET 2010

     Thank you for you assistance.

     I've learned that the problem is in Cacti, not RRDtool.  When I 
tried to reproduce the problem with a simple test case (in a standalone 
shell script), the problem disappeared.

     In looking at the Cacti debug logs, I can see that Cacti is not 
reporting the value for "files" to "rrdtool update ..." for some 
reason.  I'm still trying to figure out why (as the GUI looks correct to 
me, and all the other values work fine).  The fact that "files" is so 
much larger than the other numbers was just a coincidence that led me in 
the wrong direction.

     For the archives: if you're getting a NaN in Cacti then follow this 
HowTo for troubleshooting:


Thanks Again,

P.S.> The "official" link for that Cacti HowTo is broken: 

On 12/23/2010 05:24 AM, Simon Hobson wrote:
> Derek Simkowiak wrote:
>>      My version of that graph *almost* works.  Everything works,
>> except that the "files" count is always NaN.
> If your data is NaN then you can't expect to get a sensible graph.
> RDD tools do not care what your values are - it will not mangle one
> DS because it's different in magnitude to others. Nor will graph barf
> on it - as you suggest, it would simply plot the smaller values along
> the axis.
> Since you have given zero clue as to what you have defined and what
> you are feeding in, it's impossible to diagnose further.
> Can you post :
> The command used to create the rrd file.
> The values you are updating the file with.
> What you get out.
> What you expected to get out.
> With that information we should be able to help.

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