Creating an EagerZeroedThick disk with PowerCLI

Hey…. -  that is not possible – I hear you say – well in principle you are right. Up until today…

By mistake of course – I found that there was a change made to the 5.1 release of PowerCLI – but this change has not been documented anywhere – which I think is a shame. This post is the only public reference I know of.

Up until the 5.1 release you could not create an EagerZeroedThick hard disk with PowerCLI. Let’s look at the 5.0 documentation for PowerCLI.


As you can see above the options are Thin or Thick and if you go to look at the
VirtualDiskStorageFormat – Enum you will see the that there is no EagerZeroedThick option.


The PowerCLI changelog has a new Cmdlet Move-Harddisk – which as you can see allows you to migrate a VMDK from one location to another – and if you also noticed..

5.1 New-Harddisk

Yep, EagerZeroedThick is one of the options as you can see above. The VirtualDiskStorageFormat – Enum was not updated though.

So I used this today as part of a bigger automation process to prepare some VM’s for Oracle RAC (which I will post about in the not too distant future)

get-vm $vm1 | New-HardDisk -DiskType flat -CapacityGB 2 -StorageFormat EagerZeroedThick -Datastore $dbds |New-ScsiController -Type ParaVirtual -BusSharingMode NoSharing

Which is so much easier than… (taken from Luc Deken’s post)

$vmName = <vm-name>
$vCenter = <vCenter-name>
$esxAccount = <ESX-account>
$esxPasswd = <ESX-password>

function Set-EagerZeroThick{
	param($vcName, $vmName, $hdName)

# Find ESX host for VM
	$vcHost = Connect-VIServer -Server $vcName -Credential (Get-Credential -Credential "vCenter account")
	$vmImpl = Get-VM $vmName
	if($vmImpl.PowerState -ne "PoweredOff"){
		Write-Host "Guest must be powered off to use this script !" -ForegroundColor red
		return $false

	$vm = $vmImpl | Get-View
	$esxName = (Get-View $vm.Runtime.Host).Name
# Find datastore path
	$dev = $vm.Config.Hardware.Device | where {$_.DeviceInfo.Label -eq $hdName}
		return $false
	$hdPath = $dev.Backing.FileName

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

# Convert HD
	$vDiskMgr = Get-View -Id (Get-View ServiceInstance -Server $esxHost).Content.VirtualDiskManager
	$dc = Get-Datacenter -Server $esxHost | Get-View
	$taskMoRef = $vDiskMgr.EagerZeroVirtualDisk_Task($hdPath, $dc.MoRef)
	$task = Get-View $taskMoRef
	while("running","queued" -contains $task.Info.State){

	Disconnect-VIServer -Server $esxHost -Confirm:$false

# Connect to the vCenter
	Connect-VIServer -Server $vcName -Credential (Get-Credential -Credential "vCenter account")
	if($task.Info.State -eq "success"){
		return $true
		return $false

Set-EagerZeroThick $vCenter $vmName "Hard disk 1"

Ah the little things…..

I wonder what other gems are hidden deep in the bowels of PowerCLI that were not updated in the changelog/release notes?? …. What do you think ??