# [rrd-users] Re: Calculating a 5%-rule

Kathy Kessey kkessey at excitehome.net
Thu Feb 14 18:13:27 MET 2002

```
If you don't want to keep 30 days worth of individual samples, determine
how many samples make up a month (5 minute samples, 30 days = 8640), take
5 percent of that (432), save off that many (432) samples, each day
recalculate the top (432) to be saved.  At the end of the month, you have
the top 5% samples.  The lowest one = 95th percentile.  We ran into this
not wanting to redo 100,000+ RRDs to keep 30days of data.

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Kathy Kessey                  kkessey at excitehome.net
Excite at Home                   650.556.5087

On Thu, 14 Feb 2002, David Gabler wrote:

>
> I have done this.
>
> It is really called 95th Percentile
>
> The psudocode is to
> rrdtool fetch all the data for the past 30 days.
> figure out how many data points you have
> pop off the top 5%
> pop off the top# and there you go.  that is your 95th Percentile.
>
> David
>
> > -----Original Message-----
> > From: Geert van der Ploeg [mailto:geert at triple-it.nl]
> > Sent: Thursday, February 14, 2002 8:46 AM
> > To: rrd-users at list.ee.ethz.ch
> > Subject: [rrd-users] Calculating a 5%-rule
> >
> >
> >
> > Hi all,
> >
> > I'm implementing a sort of bandwidth-usage billing system,
> > using RRDtool.
> >
> > <short mode>
> > How to calculate what value is the highest, after ignoring
> > the highest 5% ?
> > </short mode>
> >
>
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