Physical Memory Volumes reporting incorrectly for net-snmp Linux nodes

Hello everyone,

I would like to preface my saying I am very new to Solarwinds so if there is something obvious I am doing wrong I apologize. Basically, I have SolarWinds reporting the memory used for a node on the dashboard (the gauge) and the physical memory as a volume, but the physical memory volume is incorrect, reporting nearly 100% space used. The volume appears to be taking into account the cached and shared memory. Most of the forums I've seen report the opposite, with the volumes being correct and the gauge/dashboard being wrong. This is only happening with Linux nodes using net-snmp. Is there any way to have them both report accurately, or will one always be right at the expense of the other?

Thanks for any help!

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FormerMember

Linux loves to use the RAM it can, for caches and shared mem. That's just what happens unless you tune that out.

If you want to see just the hard-allocated RAM instead of the opportunistic stuff it can reap and reallocate if need be, you'll have to do some math (I'm a nagios guy so I'm not sure that's possible here).

I skip a lot of that. Set your logic so that it'll report is physical RAM is 100% and swap is some number that sounds bad. If you're not eating like 5-10% of your swap, maybe your machine isn't really living on the edge anyway. :-D

stuartd

This is an issue with how Linux (or any *nix based system) uses / displays memory. For full background then check out this blog: Linux Ate My RAM

Essentially what you need to do is create a custom poller (or find one in THWACK) that matches the hardware in question [ALL SETTINGS > MANAGE POLLERS]. For us, net-snmp devices are most typically Checkpoint firewalls.

Anyway, first you need to find the OIDs for your hardware and specifically you need them for CPU (not relevant to your question but when creating a poller a memory one can only be created in conjunction with CPU), and also for Total Real Memory (memTotalREAL); Free memory (memFreeReal) and then you need to create a calculation.

So for the Used Free Memory your poller and calculation would be like this:

As you don't mention what the device is (net-snmp is just a generic identifier) then I can't help with the OIDs you need, but you could do an SNMP walk of your device and see if the above OIDs work for you.

Come back if you need more help or even a step by step walkthrough or if you have the same hardware as us I could export our poller and you just import at your end.