[mrtg] Re: Help - Clarification Sought

[Daniel J McDonald]

> From: Tony Hughes
> Sent: Sunday, February 25, 2001 4:59 PM
> To: mrtg at list.ee.ethz.ch
> Subject: [mrtg] Help - Clarification Sought
>So I am going to go with the
> harder way,
> which is ask for clarification on a few points and concepts.
>

You've done well...

> .wfResourceTotalEntry.wfResourceTotalCpuUsed
> which has a definition of:-
> "The amount of CPU used by all the entities on this slot in
> centiseconds
> since the slot started"

> I created a cfg file using the CpuUsed OID and another that
> returns O thus:-
> Target[mbah.cpu]:
> 1.3.6.1.4.1.18.3.3.2.5.7.1.2.1&1.3.6.1.4.1.18.3.1.4.2.1.5.1:pu
> blic at 10.208.8.2
> MaxBytes[mbah.cpu]: 100
>
> My question is how do I know that the value I am graphing is
> the actual
> percentage of cpu utilisation?

Well, that's the mib definition.  It is defined as 100ths of seconds of CPU
used.  So, if in 300 seconds of elapsed time, the processor used 7500
centiseconds of cpu processing, mrtg would divide 7500 by 300, and come up
with 25.  That means an average of 25% utilization over those 300 seconds
(or five minutes).

So, your existing config works perfectly.

>I think that the % cpu utilisation should be something like
> Percentage Used = CpuMax - CpuIdle*100/1.

Not quite.  You don't care about the total cpu since the box booted.
Instead you would need  (CpuMax - CpuMaxOld) - (CpuIdle - CpuIdleOld)
Nortel has also done the multiplication for you by measuring in
centiseconds - very clever of them.
But this number should be exactly equal to (CpuUsed - CpuUsedOld)


> If so then how do I do the maths?  I know this is a relatively simple
> concept to understand, but the OID definitions are confusing to me as
> CpuUsed is simply a number on its own unless referenced
> against CpuMax.

Ah, but you know what the change in CpuMax is going to be for any given
duration - 100 centiseconds per second.  Since MRTG is measuring deltas
CpuMax becomes irrelevant.

> I apologise for the long posting, but I need to get my tiny
> brain around this concept.

Hopefully we have enlightened you a bit.  Just remember cpuMax is a red
herring...
Daniel J McDonald - CCIE 2495, CNX
Principal Network Specialist
Digicon Technologies
http://www.digicontech.com
dmcdonald at digicontech.com

Digicon - A Cisco Systems Partner, Silver Certified.


--
Unsubscribe mailto:mrtg-request at list.ee.ethz.ch?subject=unsubscribe
Archive     http://www.ee.ethz.ch/~slist/mrtg
FAQ         http://faq.mrtg.org    Homepage     http://www.mrtg.org
WebAdmin    http://www.ee.ethz.ch/~slist/lsg2.cgi