[rrd-users] xff and heartbeat

Ehrentraut, Diana dehrentr at debis.com
Tue Sep 26 19:05:49 MEST 2000

Hi all,

as a newbie I have some problems in understanding the consolidation
After reading the tutorial, the manuals and some mails in the mailinglist I
think I understand it more or less. But I would be very greatfull if someone
could verify that.

   The heartbeat defines the period within which should be an update,
otherwise there 
   will be an *UNKNOWN* asumed.

   The xff defines how many *UNKNOWN* samples within the consolidation
interval (set by "steps" in
   RRA?) can appear until an *UNKNOWN* and not the consolidated value is
stored to the RRA.
   E.g. xff=0.5 => Only if there are 6 *UNKNOWN* out of 10 samples an
*UNKNOWN* is stored.
        xff=0.0 => All *UNKNOWN* are stored.

So, if I set my heartbeat to a very long period, the xff does almost have no
effect. On the other hand, if I set the heartbeat to a short period (e.g.
the step-size of the RRD) I will have a high probability of getting
*UNKNOWN* samples. Which I can decrease again setting xff high (e.g.

Sorry for the strange way of summing it up, but I hope someone can
understand it and tell me if I finally understood it right.

Thanks in advance,

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