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Linux Memory Utilization

We have begun using Linux boxes in our environment in the last year and I am finally getting around to monitoring them with Orion (7.7). I have been able to get SNMP on the boxes (Red Hat Enterprise AS 3.0) up with a minimal config and I have been able to add them to Orion. The list resources dialog contains all of the usual system options (CPU, Disks, Memory, Interfaces) and when selected, Orion monitors them. Now one of these Linux boxes has 9gb of physical memory, but Orion only shows the system having 2gb of real memory. I also have two other linux boxes with 4gb of physical memory. These boxes also only show 2gb of physical memory. The SNMP package on the Linux servers is Net-SNMP 5.0.9-2.30E.15. While I know this subject has been touched on before here, I have been unable to find any posts with a resolution to this issue. I will admit to not being very SNMP savvy, and all the docs I have found online are not written for the beginner.
Thanks!
Jonathan LeMaster

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jimmo

Hi Jonathan!

Get used to the fact that the values Orion reports are not easy to interpret, particularly with Linux. Better yet, consider the fact that the values reported from Linux machines are usually wrong. The problem (among others) is that SolarWinds says that Net-SNMP 5.0.9 is "known to work" and "recommend" that people install it. However, it is almost three years old and much has changed since then. Further, Orion reads an OID that was already deprecated when 5.0.9 released. So, they read an OID that was outdated even before the outdated net-snmp version they recommend.

The bottom line is that Orion reads values that are not very accurate. This has been reported to Orion support and they are planning to add a feature where users can specify their own values to read. Hopefully that will be implemented correctly and solve a lot of our problems.

It would be helpful if SolarWinds would just tell us exactly what OIDs are being read, but I have not had any luck getting this out of them. It's not like it is a state secret and it is very easy to find out ourselves.

Either run snmpd on the Linux host in debug mode (e.g. start it with "-Ddumpx_recv") or capture the traffic between the two hosts with a sniffer program (e.g. Ethereal or tcmpdump ). I started snmpd in debug mode and looked through the logs as it was easier than installing extra software. You can then see what OIDs are being read and query them yourself (snmpget or snmpwalk from the local machine). You can then see what net-snmp says the values are. Is Orion reporting these values incorrectly as well, or does the agent have a problem.

Sorry, I cannot give you a specific answer as I have not encountered that problem myself.

Regards,

Jim Mohr

Isaac

Hi Jonathan,

I would turn the MIB browser or some other SNMP querying tool loose on your linux boxes to see if the MIB is reporting the right data in terms of the memory on each box.

My guess is you will see 2GB of memory being reported by the MIB.

You want to look for the hrMemorySize value.
OID: 1.3.6.1.2.1.25.2.2

Be fantastic.

Emir

FYI, this may not be directly related but since you are monitoring a Linux system you may find this useful. We just put in a feature request to disable "shared memory" and "cached memory" from auto-discovery in Linux systems. Please upvote if you find this feature request useful.

Link: thwack.solarwinds.com/.../inhibit-the-auto-discovery-of-cached-memory-and-shared-memory-in-linux-systems