[mrtg] Re: mrtg for home users: more precision than'5minuteaverage'?

Constantine A. Murenin mureninc at gmail.com
Fri Mar 31 17:21:45 MEST 2006

On 31/03/06, PAUL WILLIAMSON <pwilliamson at mandtbank.com> wrote:
> >>> "Constantine A. Murenin" <mureninc at gmail.com> 03/31/06 3:56 AM >>>
> > >> Have you even *tried* using RRDTool as the backend and MRTG with
> > >> interval set to 1?  MRTG is not going to do 1 minute intervals, any
> > >> time soon, if ever.
> > >
> > > Can mrtg still plot my graphs and generate html in this fashion
> using
> > > most of my existing configuration?
> Yes, but you'll need to regenerate your databases (logs under "native"
> MRTG, .rrd under RRDTool) because the current resolution of
> 5 minutes will still be there.  You'll need to restart MRTG once you've
> installed RRDTool and set the interval to 1.

Are you saying that I'll only need the following:
1. Install RRDTool from a package of my OS
2. Add one additional line to my script that generates mrtg.cfg, so
that RRDTool format is used instead ('LogFormat: rrdtool')
3. It'll all work as it did before, only without the previously gathered data

Or is anything more required? From what I've read, it doesn't look
this simple for reasons unknown to me... I don't want any extra CGI, I
just want 1 minute or 30 seconds querying of my modem, I don't care
how the data is stored etc. I want mrtg to continue generating HTML
and PNG just as it does today, but with higher accuracy.

Also, is it possible to convert the current data I have with
'Interval: 5' into RRDTool's 'Interval: 1', obviously keeping the
accuracy of the old data at the old level, but having the newly
collected data with the new accuracy of 1 minute?

> > > I believe that you're thinking of MRTG as being more than it is.
> > > is a collector. It collects data.
> > > The data collected by MRTG can be stored in log files or RRD files.
> If
> > > you want one minute granularity, then you need to use RRDs.
> > > HTML is generated by the front-end to MRTG, be it the 14all.cgi
> > > included with MRTG or Routers2.cgi.
> >
> > I don't know what you are talking about. I use mrtg for everything,
> > and my configuration shell script only calls cfgmaker, indexmaker
> > and then finally mrtg. After I run this simple 50-line script once
> > on any machine with package 'mrtg' installed, and it just works.
> > But it does not provide the required accuracy, i.e. the generated
> > graphs do not show the peak usage when someone downloads a
> > ~20 mebibytes of data through 3.0/512 ADSL line through ZyXEL
> > 660.
> Neither will 1 minute intervals.  You need to set up snmp on your
> router to send a trap when your line has reached maximum capacity.
> That is the ONLY was you'll get this.  Not even a 1 second polling
> granularity will give you this information.  And in going down to
> 1 second, you've introduced a TON of potential errors.

You misunderstood what I'm after -- there is no reason for me to care
that the line has reached it's maximum capacity, the only thing I care
is that it actually does and for some extended periods of time.

I don't want the graph to jump around every second, but I want ~10MB
or 20MB downloads to be noticeable on the graph as having their actual
speed. I.e. something like 30 seconds interval is my best wish. You
see, whereas one would care of the 24-hour picture of a busy router,
with home modem for a small group of users you only care for about
~4--8 hours a day, and thus you must have greater accuracy for the
graph to actually be meaningful, IMHO.


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