Linux/Unix Volume or Disk Percent Used Issue

FormerMember

So far, all of the server monitoring tools that I have worked with, or tested, have the same issue with monitoring Linux/Unix mount points.  The problem is that the monitoring software reports the percent used to be much less than it really is, and depending on the size of the mount point, the percentage can be off by as much as 5% or more.

After investigating why this was occurring, I found out that the "inode" usage was not included in the calculations.  For example, compare the percent used from Orion to that of a 'df' command.  A 'df' command will include the inode usage when reporting percent used.

Here is how most monitoring software calculates a disk usage percentage, and my guess is that Orion uses the same calculation:

• (StorageUsed (.1.3.6.1.4.1.2021.9.1.8) / StorageSize (.1.3.6.1.4.1.2021.9.1.6)) * 100.0 

When looking at the calculation, one would think the percentage would be correct, but it is not.  To be fair, this is not SW's fault.  The issue is with net-snmp.

Anyway, for me, this way of reporting percent used is unacceptable, so I started looking for a workaround.  I found that workaround, and here's what I did:

1. Added 'includeAllDisks 10%' to a single line in snmpd.conf in the disk section
2. Created a UnDP using this OID:  diskPercent (.1.3.6.1.4.1.2021.9.1.9)

Note 01: The percentage listed in step one has nothing to do with your thresholds.  It's just used as a flag in snmp.  Therefore, the percentage can be anything you want.  It won't have any affect in Orion.

Note 02: The OID in step 2 will not be available if the line in step 1 is not added to snmpd.conf.

I have included a screenshot to show you the percentage differences below.  The stats come from an Oracle database server with numerous mount points.  If you look closely, you'll also see that Orion lists a couple of mount points twice (/u11 and /u51).  Not really sure why it does that.  The server OS is 2.6.9-67.0.1.ELsmp i686 i686 i386 GNU/Linux.

So it would be really nice if Orion could give you a choice of how you want to monitor your Linux/Unix mount points.  I don't mind adding a UnDP, but having the diskPercent OID incorporated into the program as an option would be very helpful.

Hope this helps,

- John

Congo

Thank you for the insight! We run into this problem all the time, as we are 90% *nix based. Correcting for the 'fudge factor' is very tough, but this looks to do the trick nicely.