[mrtg] SNMP Disk Space Negative Values

Christian Arnaut n8tgc at msn.com
Wed Nov 26 15:50:33 CET 2014

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!

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. * iso.
iso. = STRING: "C:\\ Label:"
iso. = STRING: "E:\\ Label:"
iso. = INTEGER: 4096
iso. = INTEGER: 4096
iso. = INTEGER: 10350335
iso. = INTEGER: -268468737
iso. = INTEGER: 6261795
iso. = INTEGER: -527400222
With the E: drive, iso. 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!

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