To be honest this have existed for years, and written about back in 2014. Now, in 2017, SCOM 2016 UR2 is released the problem remains. Perhaps with greater consequence due to virtualization.
If you’re unfamiliar with the problem SCOMpercentageCPUTimeCounter.vbs (.ps1 in SCOM 2016) is a script included in the “System Center Core Monitoring” management pack, and is used as the data source for a rule and a monitor to determinate agent health by gathering ‘HealthService’ CPU usage. The rule and monitor are set to run at a fixed interval of 321 seconds (I assume the person who wrote the MP just tapped 3-2-1 on their numpad 🙂 ) and sync time set to 00:00
Running this script every 5 minutes isn’t exactly a problem when you have physical servers or a small amount of virtual machines on your Hypervisor. But if you run 100 or 300VM’s on one host and each single VM start this script simultainiasly it will create it creates unnecessary load on your host. If this host is overcommitted as well CPU wait time could cause a ‘freeze’ on your tenant machines as well.
To illustrate the problem, I have attached a graph, that clearly show spikes during script execution.
On a monitored computer you will see a cscript.exe process executing the following command line “c:\windows\system32\cscript.exe” /nologo “SCOMPerventageCPUTimeCounter.vbs
Unfortunately out of the box there isn’t much to do. Sync time and interval is the only overridable parameters, and these will only help reduce the load on the agent machine itself. So if you experience CPU utilization peaks due to this script, I see only two options
- Disable the rule and monitor
- Then you will have to rely on the CPU utilization monitor from the operating system management pack
- Create a new rule and monitor, using SpreadInitializationOverInterval parameter
- Reduces load as executions occurs randomly within the set interval
- Requires authoring skills, but possible. Some information here.
To not let this go into oblivion, I have left feedback on Operations Manager user voice. Hopefully, Microsoft will make some changes in the future. If you have suggestions or other experience please let me know and i will update accordingly.