Using Hyper-V to Automate VHDx Optimization

Another Hyper-V Post after I ran out of storage on my Windows 10 Hyper-V Host.

TLDR: Full Script on GitHub

The idea here was to create a script to run that would clean up each of the VMs (but only the ones I wanted), shut them down, compact the Virtual Hard Drive File (VHDx File), the boot up the VM again. I had started doing this manually after finding a blog post from Garth.

High Level Overview

Get all VMs on Host that match criteria that the VM is current On and that the VM Name (In Hyper-V) does not match Server.

$VMs = Get-VM | Where-Object {$_.State -eq "Running" -and $_.Name -notmatch "Server"}

Once we have that infomration, we go a bit deeper by looping through each one using a ForEach

Foreach ($VM in $VMs)
    {
    if (Get-VMSnapshot -VMName $VM.Name){
        Write-Host "$($VM.Name) has SnapShots, remove first then re-run" -ForegroundColor Yellow
        }
    else{

        #More Code...
        }
    }

First we check if there is a snapshot, if there is, we move on to the next one. Sure we could automatically delete the snapshots too.. but they might be there for a reason, and I don’t want to willy nilly delete them all.

If they don’t have a snap shot… I get the IP Address assigned to the VM

$IPAddress = (Get-VM -Name "$($VM.Name)" | Select -ExpandProperty networkadapters).IPAddresses | Select-Object -First 1
Write-Host "$($VM.Name) | $IPAddress" -ForegroundColor Magenta

Then as long as your DNS is setup properly, you can get the Machine’s Windows Name from DNS. I then have it run a remote powershell script to do cleanup. The Script is in the $RemoteScript variable.

$VMNetName = [System.Net.Dns]::GetHostByAddress($IPAddress).Hostname
Write-Host "$($VM.Name) = $VMNetName | $IPAddress" -ForegroundColor Magenta
Invoke-Command -ScriptBlock $RemoteScript -ComputerName $VMNetName -ErrorAction Stop

Remote Script Example which deletes Branch Cache & CCM Cache Items.

$RemoteScript = 
{  
Clear-BCCache -Force
$CMObject = New-Object -ComObject 'UIResource.UIResourceMgr' 
$CMCacheObjects = $CMObject.GetCacheInfo() 
# Delete Cache item 
$CMCacheObjects.GetCacheElements() | ForEach-Object { 
    $CMCacheObjects.DeleteCacheElement($_.CacheElementID)
    }
}

Once that is done, we confirm that it has a VHDx and not a passthrough drive then shut down the VM

$VHDXPaths = $VM.HardDrives.path | Where-Object {$VM.HardDrives.DiskNumber -eq $null}
        if ($VHDXPaths){
            Get-VM -Name $VM.Name | Stop-VM -Force

Once the VM is off, we optimize it.

ForEach ($VHDXPath in $VHDXPaths)
  {
  $SizeBefore = (Get-Item -Path $VHDXPath).length
  Write-Host " Size of $((Get-Item -Path $VHDXPath).Name) = $($SizeBefore/1GB) GB" -ForegroundColor Green
  Write-Host " Optimzing VHD $VHDXPath on $($VM.Name)" -ForegroundColor Green
  Optimize-VHD -Path $VHDXPath -Mode Full
  $SizeAfter = (Get-Item -Path $VHDXPath).length
  $Diff = $SizeBefore - $SizeAfter
  Write-Host " Size After: $($SizeAfter/1GB) GB | Saving $($Diff /1GB) GB" -ForegroundColor Green
  }
Get-VM -Name $VM.Name | Start-VM

When running the script, you’ll see output like, I’ve boxed the space savings. In this example I’ve only compacted the VHDx files, I didn’t do any cleanup first.

Full Script on GitHub, grab it and edit it for own needs.

To watch it in motion, check out the script running on YouTube.

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Additional Hyper-V Posts

• How to Shut down VMs and Restart a Hyper-V Server
• How to Install a CentOS 7 Linux Virtual Machine in Windows Hyper-V Server
• Hyper-V Automate Test VMs
• Effects of Endpoint Protection on Hyper-V Server Performance
• Configuration Manager, Endpoint Protection, and Hyper-V

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