[mrtg] Re: Business Hours and 95%ile.

Forthofer Russ Russ.Forthofer at ssfhs.org
Thu Sep 6 23:41:01 MEST 2001

Thanks for the clarification.  I was unaware that the zero values were
typically ignored.

As others have also indicated, I would like to see the data presented with
just the business day, but also for the entire day.  With the knowledge you
provided, though, it seems it should be pretty straightforward to simply
create another instance of the graph - either by selectively copying the
data or by setting up cron as you suggest.



-----Original Message-----
From: Jay Hennigan [mailto:jay at west.net]
Sent: Thursday, September 06, 2001 4:37 PM
To: Forthofer Russ
Cc: mrtg at list.ee.ethz.ch
Subject: Re: [mrtg] Re: Business Hours and 95%ile.

On Thu, 6 Sep 2001, Forthofer Russ wrote:

> Jay:
> You are probably right that the "business hours only" is not for everyone.
> I would agree that in using MRTG to look for anomalies in utilization you
> want to look at the whole day.  However, IMHO, there are some cases where
> can be quite helpful to look only at the business day.  For example, if a
> line is used primarily during business hours, average utilization across a
> 24-hour day is pretty meaningless.  Average utilization and 95th
> utilization across the business day, however, can be useful statistics,
> especially in terms of gathering historical data and tracking growth.  If
> the business day "average" is what is being sought (in my case it is),
> simply zeroing out the non-business hours does not resolve the issue, as
> zeroes would skew the average.

There are settings in MRTG to control this behavior.

   Log unknown data as zero instead of the default behaviour of repeating
   the last value seen. Be careful with this, often a flat line in the
   graph is much more obvious than a line at 0.

   Normally we ignore all values which are zero when calculating the
   average transfer rate on a line. If this is not desirable use this

It would seem that if you run from cron, set the crontab for the intervals
you want, set "unknaszero" and do NOT set "withzeroes" that your averages as
shown on MRTG will indeed reflect just the business hours.  The graphs will
be zeroed out during non-business hours.

95th percentile is a different story.  It will plot the zeros unless you
hack it, but this probably won't affect the results if the 5% peak timeslots
are within business hours.

Jay Hennigan - CCIE #7880 - Network Administration - jay at west.net
NetLojix Communications, Inc.  -  http://www.netlojix.com/
WestNet:  Connecting you to the planet.  805 884-6323

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