Peter A. Menzel <[email protected]> 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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