Re: ***SPAM(-2.9)*** Disk space being incorrectly reported.

On 30 August 2011 14:20, David <[email protected]> wrote:
> As of net-snmp 5.7 disk space is incorrectly reported.

Actually, I think the disk space values are correct.
It's the calculation of percentage used that's failing


> UCD-SNMP-MIB::dskTotal.4 = INTEGER: 219227030
> UCD-SNMP-MIB::dskAvail.4 = INTEGER: 153871682
> UCD-SNMP-MIB::dskUsed.4 = INTEGER: 47817186

  219227030 / (1024*1024) = 209.07
  153871682 / (1024*1024) = 146.74
   47817186 / (1024*1024) =   45.60

which match the results from df

> Filesystem       Size    Used   Avail Capacity  Mounted on
> /dev/mfid0s1f    209G     46G    147G    24%    /usr


>  Any ideas what is going wrong here.

The calculation of the percentage usage is as follows:

   static int _percent( value, total )  {
       return (int)  (value * 100 / total );
   }

(ucd-snmp/disk_hw.c:250-ish)

Your problem is almost certainly an arithmetic
overflow when multiplying the main value by 100.
What happens if you tweak this line to read

       return (int) ( value /   (total / 100));

?
The result should be the same, but without the
possibility of overflow.

Dave

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