Category: Virtualization

Situation

You have a set of VMs that are not running at their preferred node due to maintenance or some kind of outage triggering unscheduled migration. You have set one (and just one) preferred host for all you VMs. You have done this because you are want to balance your VMs manually to guarantee a certain minimum of performance to each VM. By the way, automatic load balancing cannot do that, there will be a lag between a usage spike and load balancing if load balancing is required. But I digress. The point is, the VMs are not running where they should, and you have not enabled automatic failback because you are afraid of node flapping or other inconveniences that could create problems. Hopefully though, you have some kind of monitoring in place to tell you that the VMs are restless and you need to fix the problem and subsequently corral them into their designated hosts. Oh, and you are using Virtual Machine Manager. You could do this on the individual cluster level as well, but that would be another script for another day.

If you understand the scenario above and self-identify with at least parts of it, this script is for you. If not, this script could cause all kinds of trouble.

Script Notes

• You can skip “Connect to VMM Server” and “Add VMM Cmdlets” if you are running this script from the SCVMM PowerShell window.
• The MoveVMs variable can be set to $false to get a list. this could be a smart choice for your first run.
• The script ignores VMs that are not clustered and VMs that does not have a preferred server set.
• I do not know what will happen if you have more than one preferred server set.

The script

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#    \/____/   \/_/   \/_____/   \/_____/   \/_____/   \/_____/   \/_/\/_/   \/____/   \/_____/   \/_____/   \/_/ /_/ #
#                                                                                                                     #
#                                                   http://lokna.no                                                   #
#---------------------------------------------------------------------------------------------------------------------#
#                                          -----=== Elevation required ===----                                        #
#---------------------------------------------------------------------------------------------------------------------#
# Purpose: List VMs that are not running at their preferred host, and migrate them to the correct host.               #
#                                                                                                                     #
#=====================================================================================================================#
# Notes:                                                                                                              #
# There is an option to disable VM migration. If migration is disabled, a list is returned of VMs that are running at #
# the wrong host.                                                                                                     #
#                                                                                                                     #
#######################################################################################################################



$CaptureTime = (Get-Date -Format "yyyy-MM-dd HH:mm:ss")
Write-Host "-----$CaptureTime-----`n"
# Add the VMM cmdlets to the powershell
Import-Module -Name "virtualmachinemanager"

# Connect to the VMM server
Get-VMMServer –ComputerName VMM.Server.Name|Select-Object Name

#Options
$HostGroup = "All Hosts\SQLMGMT\*" #End this with a star. You can go down to an individual VM. All Hosts\Hostgroup\VM.
$MoveVMs = $true #If you set this to true, we will try to migrate VMS to their preferred host.
#List VMS in the host group
$VMs = Get-SCVirtualMachine | where { $_.IsHighlyAvailable -eq $true -and $_.ClusterPreferredOwner -ne $null -and $_.HostGroupPath -like $HostGroup }

# Process
Foreach ($VM in $VMs) 
{
    # Get the Preferred Owner and the Current Owner
    $Preferred = Get-SCVirtualMachine $VM.Name | Select-Object -ExpandProperty clusterpreferredowner
    $Current = $VM.HostName
    
    
    # List discrepancies
    If ($Preferred -ne $Current) 
    {
        Write-Host "VM $VM should be running at $Preferred but is running at $Current." -ForegroundColor Yellow
        If ($MoveVMs -eq $true)
        {
            $NewHost = Get-SCVMHost -ComputerName $Preferred.Name
            Write-Host "We are trying to move $VM from  $Current to $NewHost." -ForegroundColor Green
            Move-SCVirtualMachine -VM $VM -VMHost $NewHost|Select-Object ComputerNameString, HostName
        } 
    }
}