LucD notes

One of the interesting new features in vSPhere is vStorage Thin Provisioning. I’m not going to explain what Thin Provisioning is all about. For that you can consult several knowledgeable blogs (for example this entry on Virtual Geek) and/or books (for example Scott Lowe’s excellent Mastering VMware vSphere 4.0).

The problem I have with Thin Provisioning, is that there are a lot of existing guests and templates out there that were created with Thick VMDKs in the past. The only documented way I could find to convert these Thick VMDKs to Thin VMDKs was to use svMotion from the vSphere client.

Now that is not a solution I want to (or can) use in an automated environment.I could of course ‘emulate’ the svMotion process in a PowerShell script with the RelocateVM method, but that is in my opinion not really an ideal solution.

Luckily there is the VirtualDiskManager with some handy methods like the CopyVirtualDisk_Task method.

This method combined with the ReconfigVM_Task method ultimately gave me a working solution. With the following script I succeeded in converting a Thick VMDK into a Thin VMDK in place. My “in place” statement is of course relative, you have to have enough free space in the datastore to create a Thin version of the VMDK besides the Tick version of the VMDK. Once the reconfiguration is done you can safely remove the Thick VMDK file(s).

The guest has to be powered off for the following script to work !

$vmName = "guest-name"
$vCenter = "vCenter-hostname"
$esxAccount = "ESX-account"
$esxPasswd = "ESX-password"

$vcHost = Connect-VIServer -Server $vCenter
$vmImpl = Get-VM $vmName
if($vmImpl.PowerState -ne "PoweredOff"){
 Write-Host "Guest must be powered off to use this script !" -ForegroundColor red
 exit
}
$vm = $vmImpl | Get-View
$esxName = (Get-View $vm.Runtime.Host).Name

# For Virtual Disk Manager we need to connect to the ESX server
$esxHost = Connect-VIServer -Server $esxName -User $esxAccount -Password $esxPasswd

$vDiskMgr = Get-View -Id (Get-View ServiceInstance).Content.VirtualDiskManager
$firstHD = $true
$vm.Config.Hardware.Device | where {$_.GetType().Name -eq "VirtualDisk"} | % {
 if(!$_.Backing.ThinProvisioned){
 $dev = $_
 $srcName = $dev.Backing.FileName
 $dstName = $srcName.Replace("/","/thin_")
 $esx = Get-View $vm.Runtime.Host
 $srcDC = Get-Datacenter | Get-View
 $spec = New-Object VMware.Vim.VirtualDiskSpec
 $controller = $vm.Config.Hardware.Device | where {$_.Key -eq $dev.ControllerKey}
 switch($controller.GetType().Name){
 "VirtualBusLogicController" {$adapter = "busLogic"}
 "VirtualIDEController" {$adapter = "ide"}
 "VirtualLsiLogicController" {$adapter = "lsiLogic"}
 "VirtualLsiLogicSASController" {$adapter = "lsiLogic"}
 "ParaVirtualSCSIController" {$adapter = ""}
 "Default"{
 Write-Host "Unknown controller type"
 exit
 }
 }
 $spec.adapterType = $adapter
 $spec.diskType = "thin"

 $taskMoRef = $vDiskMgr.CopyVirtualDisk_Task($srcName, $srcDC.MoRef, $dstName, $srcDC.MoRef, $spec, $false)
 $task = Get-View $taskMoRef
 while("running","queued" -contains $task.Info.State){
 $task.UpdateViewData("Info")
 }

 if($firstHD){
 $specHD = New-Object VMware.Vim.VirtualMachineConfigSpec
 $firstHD = $false
 }
 $deviceMod = New-Object VMware.Vim.VirtualDeviceConfigSpec
 $deviceMod.device = $dev
 $deviceMod.device.Backing.FileName = $dstName
 $deviceMod.Operation = "edit"
 $specHD.deviceChange += $deviceMod
 }
}
Disconnect-VIServer -Server $esxHost -Confirm:$false

# For the reconfiguration of the VM we connect to the vCenter
Connect-VIServer -Server $vCenter
$taskMoRef = $vm.ReconfigVM_Task($specHD)
$task = Get-View $taskMoRef
while("running","queued" -contains $task.Info.State){
 $task.UpdateViewData("Info")
}

Annotation:

Line 3-4: provide an ESX account and password with root access on the ESX server

Line 8-11: the guest must be powered off for this script to work

Line 16: the VirtualDiskManager methods can only be used when connected to an ESX

Line 20: this loops through all devices and finds the Thick VMDKs

Line 24: the backing filename of the Thin VMDK is the same as the backing filename of the Thick VMDK with a “thin_” prefix

Line 29-39: this Switch construct provides the correct adapter name. Take note that the adapter names are case-sensitive

Line 41: the diskType property allows to specify what VMDK format the copy should have

Line 43: the CopyVirtualDisk_Task method creates a Thin copy of the Thick VMDK

Line 49-59: this construct creates the specification for the ReconfigVM_Task method

Line 64: the new Thin VMDKs are now connected (as backing file(s)) to the VM

Note that the script doesn’t remove the Thick VMDK files from the VM’s directory. This is a safety precaution should something go wrong with the conversion.

Note that this procedure was tested and tried in my environment and seems to work correctly. If you are going to use this script, first try it out in your test environment and make sure the guests with the Thin VMDKs are working correctly !