[rrd-users] Re: odd spikes due to early resets

[Clifton Royston]

On Tue, Feb 20, 2001 at 09:51:02AM +1030, BAARDA, Don wrote:
...
> Hence the probability of incorrectly interpreting a reset as a valid wrap
> is;
> 
> 	err_probability = (specified_max / measurable_max)
> 
> 	where:
> 
> 	measurable_max = (counter_max / step)
> 
> 	For a typical application of a 32bit counter, 1Mbps interface, and
> 5min step this works out as;
> 
> 	err_probability = ( (10^6 / 8) / ( 2^32 / 300) ) = 0.8% 
> 
> 	This is _very_ low!!! 

I have to disagree with you on this, if I understand what you are
calculating!

A probability of nearly 1% in a given sample is a very high probability
when you are doing samples on thousands of interfaces, thousands of
times per day.  

It brings the probability of invalid spikes in the data to near
certainty - which is exactly what many users are complaining about and
discussing remedies for.

  -- Clifton

-- 
 Clifton Royston  --  LavaNet Systems Architect --  cliftonr at lava.net
                  "WWJD?  JWRTFM!" - Scott Dorsey (kludge)

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