[36787] in North American Network Operators' Group
RE: What does 95th %tile mean?
daemon@ATHENA.MIT.EDU (Greg A. Woods)
Fri Apr 20 02:13:25 2001
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From: woods@weird.com (Greg A. Woods)
To: North America Network Operators Group Mailing List <nanog@merit.edu>
In-Reply-To: <Pine.BSF.4.30.0104200051250.26475-100000@shell.inch.com>
Reply-To: nanog@merit.edu (North America Network Operators Group Mailing List)
Message-Id: <20010420061033.81462BE@proven.weird.com>
Date: Fri, 20 Apr 2001 02:10:33 -0400 (EDT)
Errors-To: owner-nanog-outgoing@merit.edu
[ On Friday, April 20, 2001 at 00:52:39 (-0400), Charles Sprickman wrote: ]
> Subject: RE: What does 95th %tile mean?
>
> On Thu, 19 Apr 2001, Greg A. Woods wrote:
>
> > Neither MRTG nor Cricket (nor anything with RRDtool or anything similar
> > underlying it), in their standard released form, are truly suitable for
> > accounting purposes since they both can introduce additional averaging
> > errors. You need to keep all of the original sample data.
>
> This actually works pretty well:
>
> http://www.seanadams.com/95/
If you read that page carefully you'll note that he's using a modified
version of MRTG that doesn't average its samples. As it says:
This is a patch to add 95th percentile metering to MRTG. This is not as
simple a feature as one might think. MRTG normally saves only one day
worth of 5-minute samples. It is not possible to accurately calculate the
95th percentile without having all of the samples for a one month period.
In order to calculate the 95th percentile for a 30-day period, it is
necessary to save an entire 30 days worth of the 5-minute samples.
MRTG does not do that by default, nor does Cricket, nor will any tool
using RRDtool as an underlying database.
> There was a very similar discussion just weeks ago on the datacenter
> mailinglist as well, you all might want to peek at the archives...
Perhaps you should look again at who posted to that discussion.... :-)
--
Greg A. Woods
+1 416 218-0098 VE3TCP <gwoods@acm.org> <woods@robohack.ca>
Planix, Inc. <woods@planix.com>; Secrets of the Weird <woods@weird.com>
