[rrd-users] How to find a grafics error?

Peter A. Menzel prot_from_spam at famenzel.at
Sun Jun 14 21:17:34 CEST 2015

Hi Simon and David, 
  thank you for your hints!
  I actually found some missing update values - that means not every second a new set of values.
  Now I intent to tune the heartbeat value to 5 instead of 2,
  and step size of 1 remaining constant...
  So missing 1, 2 or 3 measures will not generate an *unknown* value in the RRD.
  Do you think that is the right way?
  Thank you and BR
Simon Hobson schrieb:
 >  Peter A. Menzel <prot_from_spam at famenzel.at> wrote:
>    > Here is the setup script:
>>  rrdtool create AgroFire.rrd --step 1 \
>>  DS:KesselTemp:GAUGE:2:U:U \
>>  ...
>>  RRA:AVERAGE:0.5:1:864000 \  
>  Can you be certain that you provide an update *every* second ?
>  You have a step size of 1, and a heartbeat value of 2. That means that 
> you can only have data 2 seconds old before it is considered unknown. 
> What isn't clear is which side of the point the decision is taken as 
> the manual says : > heartbeat defines the maximum number of seconds 
> that may pass between 
>> two updates of this data source before the value of the data source is 
>> assumed to be *UNKNOWN*.  
>  Eg, if you miss an update at time t=1 having done one at time t=0, does 
> the value become unknown at time t=2 or *after* time t=2. The difference 
> is that if you miss just one update, then in the former condition, when 
> you come to do the update at time t=2, the data from time t=0 to time 
> t=2 will be marked as unknown; but if it's the latter then the data 
> wouldn't become unknown unless you also miss an update at time t=2.
>  So firstly I would be checking to see that you are reliably doing an 
> update every second and not creating a few unknown values. You might 
> consider increasing the heartbeat value.
>  You have specified an xff value of 0.5, so you would regard a 
> consolidation as unknown if 50% of the source values are unknown. Since 
> missing one update could be marking 2 seconds worth (ie 2 primary steps) 
> as unknown, then missing an average of one update every 4 seconds would 
> result in missing consolidated data.
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