[mrtg] SNMP Disk Space Negative Values

[Alvaro Cornejo]

Hi

You can do the conversion after scaling down (divide) the value by
1,000/1,000,000 or whatever value you want by, and adjust Y-axis unit label
accordingly.

If you do have a TB drive I assume you don't (need to) care much about
counting bytes..

Regards

Alvaro

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On Wed, Nov 26, 2014 at 1:02 PM, Alex van den Bogaerdt <
alex at vandenbogaerdt.nl> wrote:

> I guess Steve is still sleeping :)
>
> Hope you don't mind I chime in.
>
> First of all: there's a good chance your bash will suffer from the same
> problem.
>
> It has to do with signed integers.  Adding one to 2147483647 results in -
> 2147483648. The next number is -2147483647, then -2147483646, and so on.
>
> Steve suggested you look at the hexadecimal representation of those
> numbers. You will notice it is .... 0x7FFFFFFF, 0x80000000, 0x80000001 and
> so on.
>
> To convert the numbers to positive numbers, too large to fit in a 32-bit
> signed integer, just add 4294967296. Your shell may not be able to handle
> this, just try bc.
>
>
> ----- Original Message ----- From: "Christian Arnaut" <n8tgc at msn.com>
> To: "Steve Shipway" <s.shipway at auckland.ac.nz>
> Cc: <mrtg at lists.oetiker.ch>
> Sent: Wednesday, November 26, 2014 3:50 PM
> Subject: Re: [mrtg] SNMP Disk Space Negative Values
>
>
> Steve,
>
> Pardon my ignorance. How were you able to convert the 'signed' integer of
> -268468737 to an unsigned value of 4026498559? If I can do that with a
> bash script, I'm halfway home!
>
>
> Thanks,
> ~Christian
>
>
> From: s.shipway at auckland.ac.nz
> To: n8tgc at msn.com
> CC: mrtg at lists.oetiker.ch
> Subject: RE: [mrtg] SNMP Disk Space Negative Values
> Date: Tue, 25 Nov 2014 22:46:58 +0000
>
> Your E: drive is insanely huge at 15TB.  Possibly something is using
> signed integers when it should be using unsigned...  The -268468737 value is
> a signed representation for the unsigned integer 4026498559 (convert to
> hex and get 0xEFFF7DFF in both cases); multiply the unsigned value by the
> cluster size and you get your 15TB.  Something is using an unsigned integer
> when it should be signed, or vice-versa. Steve Steve
> Shipways.shipway at auckland.ac.nz From: mrtg [mailto:mrtg-bounces+s.shipway=
> auckland.ac.nz at lists.oetiker.ch] On Behalf Of Christian Arnaut
> Sent: Wednesday, 26 November 2014 11:05 a.m.
> To: mrtg at lists.oetiker.ch
> Subject: [mrtg] SNMP Disk Space Negative Values Am attempting to use MRTG
> to monitor disk space on a Windows Server as I have done on multiple
> servers and workstations in the past. However, this time the local storage
> capacity on the local drive partition is nearly 15TB.
>
> It appears that I have exceeded an SNMP threshold where the integer values
> are now negative numbers. For example to monitor total space on the C:
> drive I used (simplified)... iso.3.6.1.2.1.25.2.3.1.4.2 *
> iso.3.6.1.2.1.25.2.3.1.6.2
>
> iso.3.6.1.2.1.25.2.3.1.3.2 = STRING: "C:\\ Label:"
> iso.3.6.1.2.1.25.2.3.1.3.4 = STRING: "E:\\ Label:"
> iso.3.6.1.2.1.25.2.3.1.4.2 = INTEGER: 4096
> iso.3.6.1.2.1.25.2.3.1.4.4 = INTEGER: 4096
> iso.3.6.1.2.1.25.2.3.1.5.2 = INTEGER: 10350335
> iso.3.6.1.2.1.25.2.3.1.5.4 = INTEGER: -268468737
> iso.3.6.1.2.1.25.2.3.1.6.2 = INTEGER: 6261795
> iso.3.6.1.2.1.25.2.3.1.6.4 = INTEGER: -527400222
>
> With the E: drive, iso.3.6.1.2.1.25.2.3.1.4.4 correctly shows the cluster
> size (4096). However, I am sure the total number of clusters isn't
> '-527400222'. Even if I used the absolute value of 527400222, the numbers
> don't add up to the 15TB partition size.
>
> Any suggestions? Or have I reached the limitation of MRTG for the purpose
> I am looking for?
>
>
> Thank you, in advance, for any assistance!
>
> ~Christian
>
>
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>
>
>
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