[rrd-users] average of 95th through 80th percentiles, in a sense

Alex van den Bogaerdt alex at ergens.op.het.net
Thu Jun 19 11:04:52 CEST 2008

On Wed, Jun 18, 2008 at 11:28:24AM -0500, Ryan goldberg wrote:
> Our upstream does 95th percentile billing in a weird way.  Quote:
> "Blahblah Telecom monitoring system takes and records a sample every five 
> minutes for both the in and out going data stream.  At the end of the month, 
> the samples are ranked and the top 5% of the samples are excluded and the next 
> highest 15% recorded samples are used to compute the monthly sustained usage. 

Next highest 15% means anything between 80% and 95%

Compute two percentiles: 95th and 80th.

Use the VDEFs in a CDEF to mask out uninteresting data (making it NaN).

Then compute an average of the resulting data using VDEF again. This
will only take finite data into consideration, thus data between 80%
and 95%

>   If the monthly average is larger than the base commitment level, the base 
> commitment level is subtracted from the monthly average.  The result is used 
> to bill the burstable usage.  The burstable useage rate is $blah/mps"

If computed rate > agreed rate, you pay for the difference. Easy enough
in a CDEF.
Alex van den Bogaerdt

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