Graph will be inaccurate when there is huge value

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Graph will be inaccurate when there is huge value

frankie
Hi All,

I have a rrdtool program to query the snmp and graph the network performance graph.
However , I find that those network port with huge usage (Let say more than 600Mb) , and then the graph can not reflect the actual usage of the network port. But those network port with normal usage are working fine.

I read this page (http://www.mrtg.org/rrdtool/tut/rrdtutorial.en.html#___top). I wild guess that the problem may related to Counter Wraps mentioned in the page. Any suggestion or comment on it?

Thanks,
frankie
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Re: Graph will be inaccurate when there is huge value

Kevin P. Foote

What did you set for max?

Alex has a good page about the update process and he covers the reboot
case as well which, should help you out.

http://www.vandenbogaerdt.nl/rrdtool/tutorial/rrdupdate.php

------
thanks
 kevin.foote


On Tue, 16 Nov 2010 19:47:15 -0800 (PST)
 frankie <[hidden email]> wrote:

>
> Hi All,
>
> I have a rrdtool program to query the snmp and graph the network
>performance
> graph.
> However , I find that those network port with huge usage (Let say
>more than
> 600Mb) , and then the graph can not reflect the actual usage of the
>network
> port. But those network port with normal usage are working fine.
>
> I read this page
> (http://www.mrtg.org/rrdtool/tut/rrdtutorial.en.html#___top). I wild
>guess
> that the problem may related to Counter Wraps mentioned in the page.
>Any
> suggestion or comment on it?
>
> Thanks,
> frankie
> --
> View this message in context:
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> Sent from the RRDtool Users Mailinglist mailing list archive at
>Nabble.com.
>
> _______________________________________________
> rrd-users mailing list
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Re: Graph will be inaccurate when there is huge value

frankie
Kevin,

The following is my rrdtool create template. Are there any problem on it?

rrdtool create /var/rrdtool/test.rrd -s 60 -b  `date -d '-1 month' +%s` DS:in:COUNTER:120:0:U
DS:out:COUNTER:120:0:U
RRA:AVERAGE:0.5:1:600
RRA:AVERAGE:0.5:6:700
RRA:AVERAGE:0.5:24:775
RRA:AVERAGE:0.5:288:797
RRA:MAX:0.5:1:600
RRA:MAX:0.5:6:700
RRA:MAX:0.5:24:775
RRA:MAX:0.5:288:797


Thanks,
Frankie
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Re: Graph will be inaccurate when there is huge value

oetiker
Administrator
In reply to this post by frankie
Hi Frankie,

Tuesday frankie wrote:

>
> Hi All,
>
> I have a rrdtool program to query the snmp and graph the network performance
> graph.
> However , I find that those network port with huge usage (Let say more than
> 600Mb) , and then the graph can not reflect the actual usage of the network
> port. But those network port with normal usage are working fine.
>
> I read this page
> (http://www.mrtg.org/rrdtool/tut/rrdtutorial.en.html#___top). I wild guess
> that the problem may related to Counter Wraps mentioned in the page. Any
> suggestion or comment on it?

rrdtool does recognize counter wraps in 32 and 64bit counters, but
if a counter wraps multiple times between update intervals, then
rrdtool will not be able to give accurate results anymore ... to
prevent this:

  * Use 64bit counters

  * Read counters frequently

  * If the counter wraps at odd times, use the DERIVE ds type with
    a minimum value of 0. This will cause counter wraps to cause
    'unknowns' to be logged.

cheers
tobi


> Thanks,
> frankie
>

--
Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland
http://it.oetiker.ch [hidden email] ++41 62 775 9902 / sb: -9900

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Re: Graph will be inaccurate when there is huge value

frankie
Tobi,

It works. Great.

Thanks,
Frankie