[mrtg] Re: 95th percentile?

Pete Templin templin at urdirect.net
Fri Sep 24 17:04:05 MEST 1999

On Fri, 24 Sep 1999, David C Prall wrote:

> What exactly are you looking for. I just use the WithPeak[]: wmy option.
> This shows the high along with the averages. Giving you four lines
> rather then two.
> At some point there was a patch for doing this, but at somepoint I
> believe it got converted into the WithPeak option. I have only been
> using MRTG for 6 months where I have actually looked beyond the standard
> default configmaker script. And at that point WithPeak was implemented,
> so I used it.

Most folks looking for 95th percentile want to be able to calculate the
95th percentile of all of the data over a given time period (usually a
month).  MRTG only keeps its five minutes numbers for about two days, and
then it only stores averaged averages.  It's impossible to recreate the
true 95th percentile five minute average using reaveraged numbers; the
peaks merely show the highest five minute peak across a two hour period.
There's no way to determine how many five minute samples were that high.

Some people have written scripts that archive a day's worth of five-minute
samples each day, and then crank through that unaveraged data at the end
of the month.  The few folks I've talked to about this usually wrote it on
company time, and weren't permitted to release their script.  It's
actually not that hard; the challenge is making sure that it scales well
(or can be reengineered to scale).


Peter J. Templin, Jr., CCNA
Systems and Networks Administrator

On-Line Internet Services - URDirect.net
A division of Global On-Line Computers
2414 Babcock Rd. Suite 106		templin at urdirect.net
San Antonio, TX 78229			(210)692-9911

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