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Powering on virtual machines fails with the error: MAX VCPUs limit is reached (1020121)

Symptoms

  • Powering on virtual machines fails
  • When trying to power on a virtual machine, you see the error:

Failed to power on VM
Could not power on VM : Number of running VCPUs limit exceeded.
Max VCPUs limit reached: 200 (4096 worlds)

Resolution

vSphere 4.1 has an algorithm that dynamically calculates the number of recommended vCPUs on a given host depending on the resources available. This prevents over-committing of resources.
 
If you experience this issue, you can adjust the MAXvCPU count to allow for more vCPUs.
 
Note: ESX and ESXi 4.1 allow a maximum of 512 vCPUs.

Increasing the MAXvCPU count using the vSphere CLI

Run this command to see the maximum number of vCPUs that are allowed:

# esxcfg-advcfg -j maxvCPUs
The output looks similar to:
# esxcfg-advcfg -j maxvCPUs
maxvCPUs = <number of VCPUs>

To increase the maximum number of vCPUs to 512, run the command:

# esxcfg-advcfg -k 512 maxvCPUs

If you rerun # esxcfg-advcfg -j maxvCPUs, the output appears similar to:

# esxcfg-advcfg -j maxvCPUs
maxvCPUs = 512

Increasing the MAXvCPU count using the vSphere Client

To increase the maximum number of vCPUs to 512:
  1. Launch the vSphere Client.
  2. Click the host.
  3. Click the Configuration tab, then go to Advanced Settings.
  4. Go to Vmkernel > Boot > maxVCPUS.
  5. Modify the parameter to 512.

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