Like many other places I believe, our non-prod hosts run on vSphere Standard instead of Enterprise Plus for its lower price. The price is great, but what isn’t is that DRS isn’t available. Which means every time a host needs to be put in maintenance mode you have to do it the old school way: manually vmotion all the VMs running on it.

My non-prod cluster has 9 hosts and 300 VMs. Although an option, the manual vMotion way is incredibly boring and time consuming.

In this post I am going to share a Powershell script that I quickly put together to automate the process of safely evacuating a host from the VMs running on it.

This script will safely migrate the VMs of a host one by one to other hosts by taking into consideration:

  • Projected maximum CPU usage after migration (default 75%).
  • Projected maximum Memory usage after migration (default 75%).
  • Projected maximum vCPU per physical cores after migration (default 9).
  • Possibility to exclude hosts from the possible destinations.
  • Possibility to exclude VMs from the migratees.
  • Interactive mode with possibility to change the selected destination host (default) or skip a VM.
  • Fully automated mode.
  • Possibility to use whatif.

If the resources requirements can’t be fulfilled, a warning is displayed and the VM is skipped.

The execution is pretty slow so I it’s something that can be improved. I don’t really mind as I fire it up and then I go do something else while it’s doing my job.

We could imagine adding a command to place the host in maintenance mode at the end of the script, but for now I don’t mind a right click.

Usage examples

Evacuate a host automatically with the default values (see above).

All the live VMs on ESXi-1 will be migrated to other hosts as long as they don’t go over 75% CPU/MEM usage and a 9:1 vCPU ratio.

Evacuate-VMHost -VMHost (Get-vmhost ESXi-1) -fullyautomated

Evacuate a host interactively with the defined values.

For every VM a choice will be given to the user including the projected capacity after the migration for every available host with a recommended one.

The user has 2 choices:

  • Press enter and follow the script’s recommendation (the host with a *)
  • Select another destination host
  • Skip the VM and leave it where it is
Evacuate-VMHost -VMHost (Get-vmhost ESXi-1) -VMHostMaxCPUUsagePercent 80 -VMHostMaxMEMUsagePercent 85 -VMHostMaxVCpuPerCore 10



  • VMHost: Host to evacuate
  • VMHostMaxCPUUsagePercent: CPU usage (%) limit that the destination hosts shouldn’t reach
  • VMHostMaxMEMUsagePercent: Memory usage (%) limit that the destination hosts shouldn’t reach
  • VMHostMaxVCpuPerCore: vCPU:core ration that the destination hosts shouldn’t reach
  • ExcludedVMHost: Hosts to exclude from the possible destinations
  • ExcludedVM: Virtual machines that won’t be migrated
  • fullyAutomated: No choice given to the user, the VMs are migrated automatically one by one
  • Whatif: Simulate the migration but doesn’t do it

Script code

Also available on github.

Function Evacuate-VMHost {

param (

    $VMHostMaxCPUUsagePercent = 75,

    $VMHostMaxMEMUsagePercent = 75,

    $VMHostMaxVCpuPerCore = 9,





Try {

    IF ($VMHost.connectionstate -eq "connected") {

    $VM = $VMHost | Get-VM | where {$_ -notin $ExcludedVM}

        $VM | where powerstate -eq poweredon | ForEach-Object {
            $CurVM = $_

            $PossibleHost = Get-VMHost `
                | Where name -ne $ `
                | where {$_ -notin $ExcludedVMHost} `
                | where connectionstate -eq "connected" `
                | where {(Compare-Object $ $ -notcontains "<="}

            $i = 0
            $choice = "a"

            $selectedVMHost = $PossibleHost | ForEach-Object {

                $HostVM = $_ | get-vm | where powerstate -eq poweredon

                    id = $i
                    name = $
                    "ProjectedCpuUsage" = [math]::round(($_.CpuUsageMhz + $CurVM.ExtensionData.Runtime.MaxCpuUsage) / $_.CpuTotalMhz * 100,1)
                    "ProjectedMemUsage" = [math]::round(($_.MemoryUsageMB + $CurVM.memoryMB) / $_.MemoryTotalMB * 100,1)
                    "ProjectedVCPUperCORE" =[math]::round(($HostVM | Measure-Object -Property numcpu -Sum).sum / $_.NumCpu,1)
                    "Projected#LiveVM" = $HostVM.count + 1

            } | where {$_.ProjectedCpuUsage -lt $VMHostMaxCPUUsagePercent -and $_.ProjectedMemUsage -lt $VMHostMaxMEMUsagePercent -and $_.ProjectedVCPUperCORE -lt $VMHostMaxVCpuPerCore}

            IF ($selectedVMHost) {

                $BestVMHost = $selectedVMHost | where id -eq ($selectedVMHost | select id,@{l="sum";e={$_.ProjectedCpuUsage + $_.ProjectedMemUsage}} | Sort-Object sum | select -First 1).id

                ($selectedVMHost | where id -eq $ = "*"

                IF (!$fullyAutomated) {


                    $_ | select name,powerstate,numcpu,memorygb
                    $selectedVMHost | Sort-Object id | ft -au

                    Write-Host "Select host manually by its ID"
                    Write-Host "Press enter to follow the recommendation ( * )"
                    Write-Host "Enter N to skip this VM"

                    While ($choice -notin @("","n") -and $choice -notin (1..$i)) { $choice = Read-Host " " }

                    IF (!$Choice) {$selectedVMHost = $BestVMHost}
                        ELSEIF ($choice -eq "n") {Write-Warning "$($ skipped"}
                            ELSE {$selectedVMHost = $selectedVMHost | where id -eq $Choice}

                } ELSE {
                    $selectedVMHost = $BestVMHost

                IF ($choice -ne "n") {

                    Write-Host "$($ moving to $($" -ForegroundColor green

                    $params = @{VM = $_ ; Destination = get-vmhost $}

                    IF ($Whatif) {$params.Add('whatif', $true)}

                    Move-VM @params | Out-Null


            } ELSE {Write-Warning "There is no host capable of fulfilling the destination resource requirements"}


    } ELSE {Write-warning "$($ is in a $($VMHost.connectionstate) state"}

    Write-Error $_.Exception -ErrorAction stop