VM Conversion extension in Windows Admin Center Frequently Asked Questions (Preview)

Yes, both DHCP and Static IP addresses are supported.

Static IP is supported using scripts. When a static IP is detected, the VM credentials are collected to run the script and capture the IP address details. This data persists on the target Hyper-V host after the cutover phase.

The tool automatically detects the source VM's boot type. BIOS boot creates a Generation 1 VM on Hyper-V. UEFI boot creates a Generation 2 VM on Hyper-V.

The VM Conversion tool currently migrates disks as dynamically expanding (thin provisioned) VHDX files, which means only the used portion of the disk is copied—not the full allocated size.

During migration, a VM with a provisioned size of 500 GB but actual usage of 250 GB results in a 250 GB dynamic VHDX on the destination. While this approach is space-efficient, it might cause storage management issues later.

After migration, customers should convert the VHDX to a fixed size to reflect the full provisioned storage using the PowerShell command:

Convert-VHD -Path "C:\VMs\MyDisk.vhdx" -DestinationPath "C:\VMs\MyDisk_Fixed.vhdx" -VHDType Fixed

No, the tool doesn't support migration to Azure Local. Use Azure Migrate to migrate virtual machines to Azure Local.

No, the tool doesn't support virtual machines running on vSAN.

No, the conversion tool is only available in Windows Admin Center on-premises.

During migration, memory is configured as static, even if the source virtual machine is set to use dynamic memory. This design choice to ensure migration stability and compatibility between VMware and Hyper-V memory management.

To re-enable dynamic memory of change RAM parameters after migration:

1. Open Windows Admin Center.
2. Navigate to the Virtual machines extension.
3. Power off the migrated virtual machine.
4. Select Settings.
5. Update the required memory parameters: Startup memory, Enable dynamic memory, Minimum memory, Maximum memory, and Memory buffer.
6. Save changes and power on the virtual machine.

• The Resync option, which allows data synchronization between initial replication and delta replication, isn't currently supported.

• VMware Tools aren't automatically uninstalled post-migration—remove them manually if needed.

• Hyper-V drivers must be installed on Linux machines before starting migration. Download and install Linux Integration Services v4.3 for Hyper-V and Azure.

• During virtual machine conversion, the BIOS GUID on the destination virtual machine doesn't match the source virtual machine unless it's manually updated. This behavior might affect virtual machine identity synchronization, or licensing checks that rely on consistent BIOS-level identifiers. BIOS-level identifiers must be updated in virtual machine identity synchronization, and migration.

  
  

  Expand this section and use the script provided to update the BIOS GUID on the migrated Hyper-V virtual machine.

  To update the BIOS GUID for a Hyper-V virtual machine:

  1. Extract the following script into a file named Update-VMBiosInfo.ps1.
  2. Open PowerShell as Administrator.
  3. Run the script with the required parameters: .\Update-VMBiosInfo.ps1 -VMName "VM Name" -BiosGuid "New BIOS GUID"

  <#
  .SYNOPSIS
  Updates the BIOS GUID of a specified Hyper-V virtual machine.
  
  .DESCRIPTION
  This script stops a specified Hyper-V virtual machine, updates its BIOS GUID using CIM (Common Information Model), and WMIv2 (root\virtualization\v2), and then restarts the VM. It handles both synchronous and asynchronous operations triggered by the Hyper-V Management Service.
  
  It's useful in scenarios such as VM identity synchronization, VM migration, or reconfiguration where BIOS-level identifiers are required to be updated.
  
  .PARAMETER VMName
  The name of the Hyper-V virtual machine whose BIOS GUID is to be updated.
  
  .PARAMETER BiosGuid
  The new BIOS GUID to assign to the virtual machine. The script automatically formats the GUID with braces if not provided.
  
  .EXAMPLE
  .\Update-VMBiosInfo.ps1 -VMName "Contoso" -BiosGuid "{423A2700-F96D-561B-B421-C3088111A97B}"
  
  This command updates the BIOS GUID of the virtual machine named "Contoso" to the specified GUID.
  
  .NOTES
  Author: MICROSOFT Corporation
  Version: 1.0
  Date: 2025-08-07
  Requirements:
  - Run with administrator privileges
  - Requires Hyper-V and access to the root\virtualization\v2 namespace
  - Tested on Windows Server 2019/2022 and Windows 10/11 with Hyper-V enabled
  
  .RETURNS
  Outputs success messages and job details. Throws descriptive errors if there is a failure.
  
  .LINK
  https://learn.microsoft.com/windows-server/virtualization/hyper-v/
  
  #>
  
  param (
      [Parameter(Mandatory = $true)]
      [string]$VMName,
  
      [Parameter(Mandatory = $true)]
      [string]$BiosGuid
  )
  
  # Helper function to serialize
  function ConvertTo-CimEmbeddedString {
      [CmdletBinding()]
      param(
          [Parameter(ValueFromPipeline)]
          [Microsoft.Management.Infrastructure.CimInstance]$CimInstance
      )
  
      if ($null -eq $CimInstance) {
          return ""
      }
  
      $cimSerializer = [Microsoft.Management.Infrastructure.Serialization.CimSerializer]::Create()
      $serializedObj = $cimSerializer.Serialize($CimInstance, [Microsoft.Management.Infrastructure.Serialization.InstanceSerializationOptions]::None)
  
      return [System.Text.Encoding]::Unicode.GetString($serializedObj)
  }
  
  # Stop VM
  Write-Output "Stopping VM '$VMName'..."
  Stop-VM -Name $VMName -Force
  
  # Retrieve the VMs system settings data using its name
  $vmSettingsData = Get-CimInstance -Namespace "root\virtualization\v2" -Query "select * from Msvm_VirtualSystemSettingData where ElementName = '$VMName'" -ErrorAction Stop
  
  # Ensure BIOS GUID has { } format
  if (-not ($BiosGuid.StartsWith("{") -and $BiosGuid.EndsWith("}"))) {
      $BiosGuid = "{$BiosGuid}"
  }
  # Set the BIOS GUID
  $vmSettingsData.BIOSGUID = $BiosGuid
  
  # Get the Virtual System Management Service object
  $vmms = Get-CimInstance -Namespace root\virtualization\v2 -Class Msvm_VirtualSystemManagementService -ErrorAction Stop
  
  # Apply the updated system settings using ModifySystemSettings
  $result = $vmms | Invoke-CimMethod -Name "ModifySystemSettings" -Arguments @{
      "SystemSettings" = ($vmSettingsData | ConvertTo-CimEmbeddedString)
  } -ErrorAction Stop
  
  # Check the return value to determine if the operation succeeded
  if ($result.ReturnValue -eq 0) {
      # Success: operation completed synchronously
      Write-Host "BIOS GUID successfully updated for VM: $VMName (synchronous)"
  }
  elseif ($result.ReturnValue -eq 4096) {
  
      # 4096 indicates the method started an asynchronous job
      $jobPath = $result.Job
      Write-Host "BIOS GUID update started asynchronously for VM: $VMName (job path: $jobPath)"
      # Get the job object using its path
      $job = Microsoft.PowerShell.Management\Get-CimInstance -CimInstance $jobPath
  
      # Poll the job state until it's no longer Running (4) or Starting (3)
      while ($job.JobState -eq 3 -or $job.JobState -eq 4) {
          Start-Sleep -Seconds 1
          $job = Microsoft.PowerShell.Management\Get-CimInstance -CimInstance $jobPath
      }
  
      # If job completes successfully
      if ($job.JobState -eq 7) {
          Write-Host "BIOS GUID updated successfully for VM: $VMName (asynchronous job completed)"
      }
      else {
          # Job failed or didn't complete properly
          throw "Async job failed. JobState: $($job.JobState), ErrorDescription: $($job.ErrorDescription)"
      }
  }
  else {
      # Any other return value indicates a failure
      throw "ModifySystemSettings failed with ReturnValue: $($result.ReturnValue)"
  }
  
  Write-Output "BIOS GUID successfully updated for VM: $VMName"
  # Start the VM again
  Write-Output "Starting VM '$VMName'..."
  Start-VM -Name $VMName
  

  Note

  This process updates only the BIOS GUID. The BIOS Serial Number isn't updated because VMware and Hyper-V use different formats:

  • VMware BIOS Serial Number: UUID format (8-4-4-4-12) → 503a4411-be04-bd40-98ac-ffa42335cc22
  • Hyper-V BIOS Serial Number: Custom format (4-4-4-4-4-4-2) → 3123-9812-5797-4305-8770-5953-62

  If licensing in your environment depends on a combination of BIOS GUID and BIOS Serial Number, the source, and destination values won't match, even if the BIOS GUID is manually updated.

Related content

To learn more, see the following articles:

• Overview of VMware to Hyper-V migration
• Migrate VMware Virtual Machines to Hyper-V in Windows Admin Center
• Troubleshoot VM Conversion Extension
• What's new in VM Conversion Extension