CDM not alerting for swap space on HP-UX servers when reserve/psuedo-swap is used

Products

• DX Unified Infrastructure Management (Nimsoft / UIM)

Issue/Introduction

We have several HP-UX servers configured to alert when swap space is low.

However, we are only receiving the alerts when physical swap usage meets the defined threshold, and no alerts for the reserve swap or pseudo swap.

Environment

Release : 20.3

Component : UIM - CDM WITH IOSTAT

Cause

working as designed.

Resolution

The probe is using the pstat_getswap() API which will calculate swap memory for device and file system but not "reserve" and "memory" as shown in the swapinfo command output.

From the command output, "memory" is nothing but a Pseudo swap. It is a swap space, which the operating system recognizes, but in reality it does not exist. It does not exist in memory; it does not exist on disk; it does not exist anywhere. However, the operating system does recognize it, which means more swap space can be reserved than physically exists. The purpose of pseudo swap is to allow more processes to run in memory, than could be supported by the swap device (dev and filesystem).

Here the actual swap memory is dev and filesystem only, that is the reason the probe is not counting the reserve memory data while calculating the swap memory. 

It is not possible for the CDM probe to be enhanced to monitor this memory due to the above mentioned limitations.

 

Additional Information

Please refer to the below article which will explain in detail about the swap memory (swapinfo command).

https://brainscraps.fandom.com/wiki/Understanding_Device_and_Pseudo_Swap