Hyper-V Script: Validate VHD

Hyper-V provides a handy scripting interface that allows you to validate a virtual hard disk.  You can use this for two main purposes:

1. To confirm that a standard VHD file is correctly structured and not corrupted.
2. To confirm that a differencing disk has all of its parent disks present.

Here is a sample PoweShell script:

 # Prompt for the Hyper-V Server to use

 $HyperVServer = Read-Host "Specify the Hyper-V Server to use (enter '.' for the local computer)"

 # Get name for VHD

 $VHDName = Read-Host "Specify the name of the virtual had disk to validate"

 # Get the Msvm_ImageManagementService object

 $ImageManagementService = gwmi Msvm_ImageManagementService -namespace "root\virtualization" -computername $HyperVServer

 # Validate the VHD

 $result = $ImageManagementService.ValidateVirtualHardDisk($VHDName)

 #Return success if the return value is "0"

 if ($Result.ReturnValue -eq 0)

    {write-host "The virtual hard disk is valid."} 

 #If the return value is not "0" or "4096" then the operation failed

 ElseIf ($Result.ReturnValue -ne 4096)

    {write-host "The virtual hard disk is not valid.  Error value:" $Result.ReturnValue}

   Else

    {#Get the job object

     $job=[WMI]$Result.job

     #Provide updates if the jobstate is "3" (starting) or "4" (running)

     while ($job.JobState -eq 3 -or $job.JobState -eq 4)

       {write-host "Validating. "$job.PercentComplete "% complete"

        start-sleep 1

        #Refresh the job object

        $job=[WMI]$Result.job}

      #A jobstate of "7" means success

     if ($job.JobState -eq 7)

        {write-host "The virtual hard disk is valid."}

       Else

        {write-host "The virtual hard disk is not valid."

         write-host "ErrorCode:" $job.ErrorCode

         write-host "ErrorDescription" $job.ErrorDescription}

    }

And a VBScript sample:

 Option Explicit

 Dim HyperVServer

 Dim VHDName

 Dim WMIService

 Dim Msvm_ImageManagementService

 Dim Result

 Dim Job

 Dim InParam

 Dim OutParam

 'Prompt for the Hyper-V Server to use

 HyperVServer = InputBox("Specify the Hyper-V Server to create the virtual machine on:")

 'Get name for VHD

 VHDName = InputBox("Specify the name of the virtual had disk to validate:")

 'Get an instance of the WMI Service in the virtualization namespace.

 Set WMIService = GetObject("winmgmts:\\" & HyperVServer & "\root\virtualization")

 'Get the Msvm_ImageManagementService object

 Set Msvm_ImageManagementService = WMIService.ExecQuery("SELECT * FROM Msvm_ImageManagementService").ItemIndex(0)

 'Setup the input parameter list

 Set InParam = Msvm_ImageManagementService.Methods_("ValidateVirtualHardDisk").InParameters.SpawnInstance_()

 InParam.Path = VHDName 

 'Execute the method and store the results in OutParam

 Set OutParam = Msvm_ImageManagementService.ExecMethod_("ValidateVirtualHardDisk", InParam) 

 'Check to see if the job completed synchronously

 if (OutParam.ReturnValue = 0) then

    Wscript.Echo "The virtual hard disk is valid."

 elseif (OutParam.ReturnValue <> 4096) then

    Wscript.Echo "The virtual hard disk is not valid."

 else   

    'Get the job object

    set Job = WMIService.Get(OutParam.Job)

     'Wait for the job to complete (3 == starting, 4 == running)

    while (Job.JobState = 3) or (Job.JobState = 4)

       Wscript.Echo "Validating. " & Job.PercentComplete & "% complete"

       WScript.Sleep(1000)

       'Refresh the job object

       set Job = WMIService.Get(OutParam.Job)

    Wend

    'Provide details if the job fails (7 == complete)

    if (Job.JobState <> 7) then

       Wscript.Echo "The virtual hard disk is not valid."

       Wscript.Echo "ErrorCode:" & Job.ErrorCode

       Wscript.Echo "ErrorDescription:" & Job.ErrorDescription

    else

       Wscript.Echo "The virtual hard disk is valid."

    end If

 end if

Cheers,

Ben