[rrd-users] Re: SNMP Total Traffic

Alex van den Bogaerdt alex at slot.hollandcasino.nl
Tue Jan 16 23:54:07 MET 2001

Clifton Royston wrote:
> On Mon, Jan 15, 2001 at 07:30:34PM +0100, Alex van den Bogaerdt wrote:
> > 
> > Aragon Gouveia wrote:
> > 
> > [snipped: need billing per week]
> > 
> > The average number of bytes per second, multiplied with the number of
> > seconds, gives you the number of bytes...
> > So: display exactly one week and read the average.
>   Not necessarily, depending on the prevalence of NANs stored in the
> RRD, e.g. for intervals when the device was not being queried or when
> it was unreachable.  An artifact of computing it this way is that you
> can lose the accuracy of the data by transforming it to a rate and back
> again.

On the accuracy:  I think that this is not a big issue.  Rounding will
occur way behind the decimal point and if you look at more than one
interval half of the errors will be canceled out by the other half.
So, if an error is still there, it will be around one octet.  This won't
be an issue for billing purposes.

>   The RRD will store NANs for the rate for this period; the NANs will
> be ignored when constructing the average rate for the period.  Hence
> the reconstructed data could be incorrect, because any such intervals
> will be left out of the calculation (even though the byte counter value
> before and after the interval was known), and hence the total number of
> bytes calculated in this way could be more or less than the real value.

Granted, this needs some work.  What if you turn every NaN into 0. This
way at least you know the calculation will end up being equal or lower
than the actual amount.  The customer will probably not object.

With proper settings for heartbeat and for xff, most errors won't even
show up.

 / alex at slot.hollandcasino.nl                  alex at ergens.op.het.net \
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