[mrtg] SNMP Disk Space Negative Values

[Christian Arnaut]

Thank you all for your feedback. Alex, thanks for the data. I have a thought for a solution based on the information you provided. I'll work on this towards a solution.
 
 
Thank you again,
~Christian

 
> From: alex at vandenbogaerdt.nl
> To: mrtg at lists.oetiker.ch
> Date: Wed, 26 Nov 2014 19:02:15 +0100
> Subject: Re: [mrtg] SNMP Disk Space Negative Values
> 
> 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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