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Discrepancy between LoadMaster and vCenter VM CPU Usage

 

Information

 

Summary:

Discrepancy between LoadMaster and vCenter VM CPU Usage

Environment:

Product: LoadMaster

Version: Any

Platform: Virtual LoadMaster

Application: Any

Question/Problem Description:

Why does monitoring the LoadMaster running on VMware report different CPU data than monitoring the virtual machine from the ESXi host?

Steps to Reproduce:  
Error Message:  
Defect Number:  
Enhancement Number:  
Cause:

The Home page statistics shown on the LoadMaster WUI are captured every 60 seconds. It is also important to note that the statistics shown in the historic graphs are drawn using the total average of an hour worth of CPU activity.

So the calculation for the historic graph would be done in the following way: 

  1. CPU utilization is captured every 60 seconds.
  2. This means that there will be 60 captures in 1 hour.
  3. The historic graph then takes the overall average of the 60 captures and records this as the total CPU utilization for the given hour.

 

Additionally, Guest OS (Kemp Progress LoadMaster) CPU/RAM and vCenter Virtual Machine  CPU/RAM use two different metrics. Even though they are related, they are not necessarily strictly identical as Guest OS LM doesn't know that CPU/RAM resources are shared with other VMs. Also, the metrics capture in vCenter is likely to be different from the Guest OS (more accurate as it takes multiple captures per minute) which adds a layer of complexity and increase the discrepancy between the LM metrics and the vCenter one.

Resolution:

We recommend to use the WUI home page statistics and historic graphs as the show for current and past CPU utilization levels to monitor Guest OS (Kemp Progress LoadMaster).

Workaround:  
Notes:  

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