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Since the release of vSphere, you are able to Hot Add memory and vCPU. Quote from the VMware website:

Virtual Machine Hot Add Support— The new virtual hardware introduced in ESX/ESXi 4.0 supports hot plug for virtual devices and supports addition of virtual CPUs and memory to a virtual machine without powering off the virtual machine. See the Guest Operating System Installation Guide for the list of operating systems for which this functionality is supported.

 

So I wanted to see, if I was able to enable/disable this settings via PowerCLI and came up with a couple of functions.

The first function enables the Memory Hot Add feature:

Function Enable-MemHotAdd($vm){
    $vmview = Get-vm $vm | Get-View 
    $vmConfigSpec = New-Object VMware.Vim.VirtualMachineConfigSpec

    $extra = New-Object VMware.Vim.optionvalue
    $extra.Key="mem.hotadd"
    $extra.Value="true"
    $vmConfigSpec.extraconfig += $extra

    $vmview.ReconfigVM($vmConfigSpec)
}

You can run the function via the following command:

Enable-MemHotAdd vc01

When you verify the settings in the vSphere Client, You’ll see that the Memory Hot Add feature is enabled.

There is only one problem, the setting doesn’t work. You have to shutdown and start the VM, before you are able to hot add memory to the VM. When the VM is started again, I was able to Hot Add extra memory 🙂

To add extra memory via PowerCLI, You have to run the following command:

Get-VM -Name "vc01" | Set-VM -MemoryMB "3072"

 

You can use the next function to disable the setting:

Function Disable-MemHotAdd($vm){
    $vmview = Get-VM $vm | Get-View 
    $vmConfigSpec = New-Object VMware.Vim.VirtualMachineConfigSpec

    $extra = New-Object VMware.Vim.optionvalue
    $extra.Key="mem.hotadd"
    $extra.Value="false"
    $vmConfigSpec.extraconfig += $extra

    $vmview.ReconfigVM($vmConfigSpec)
}

 

I have also created two functions which you can use to enable or disable the hot add feature for vCPU’s:

Enable:

Function Enable-vCpuHotAdd($vm){
    $vmview = Get-vm $vm | Get-View 
    $vmConfigSpec = New-Object VMware.Vim.VirtualMachineConfigSpec

    $extra = New-Object VMware.Vim.optionvalue
    $extra.Key="vcpu.hotadd"
    $extra.Value="true"
    $vmConfigSpec.extraconfig += $extra

    $vmview.ReconfigVM($vmConfigSpec)
}

Disable:

Function Disable-vCpuHotAdd($vm){
    $vmview = Get-vm $vm | Get-View 
    $vmConfigSpec = New-Object VMware.Vim.VirtualMachineConfigSpec

    $extra = New-Object VMware.Vim.optionvalue
    $extra.Key="vcpu.hotadd"
    $extra.Value="false"
    $vmConfigSpec.extraconfig += $extra

    $vmview.ReconfigVM($vmConfigSpec)
}