[mrtg] SNMP Disk Space Negative Values

Steve Shipway s.shipway at auckland.ac.nz
Tue Nov 25 23:46:58 CET 2014

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 Shipway

s.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. = 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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