LucD notes

When you try to migrate a guest, that is using one or more RDM disks, you might see this message.

The reason this is most probably because the LUN IDs are different on the source and the destination ESX server.

One solution is:

• stop the guest
• write down the Physical LUN ID
• remove the RDM disk(s)
• vMotion the guest
• add the RDM disk(s) to the guest based on the Physical LUN ID
• start the guest

But why do this the hard (manual) way when we have PowerCLI ?

Automating the above scenario doesn’t look too difficult, but there are some pitfalls on the way.

In this step I collect extensive information about the guest and the RDM disk(s) it has connected.

As a safety-measure, the collected information is dumped to a CSV file. This should allow, in case of script-failure, to restore the RDM mappings quite easily.

The collected information should also include to which controller the RDM disk is connected and the RDM’s unit number. This is important because otherwise the guest’s OS might mix up the drive lettering.

For this step I use a filter, called Remove-HD. This makes it easy to combine this in a pipe with the Get-Harddisk cmdlet.

I could have used PowerCLI’s Remove-Harddisk but this cmdlet leaves the mapping files on the datastore and thus makes your guest consume unused disk space.

The filter has two steps, the first one removes the RDM from the guest’s configuration (ReconfigVM_Task) and the second step removes (DeleteDatastoreFile_Task) the mapping file(s) from the datastore.

This function (New-RawHardDisk) already appeared in the PowerCLI Community thread Adding an existing hard disk. I just added some logic to be able to add physical and virtual mode RDMs.

This is driving part of the script. It controls the logic and the order in which the different functions and filters are called.

# ESX server against which you want to execute the script
$tgtESX = "My-target-ESX-host"

# Attach a RDM disk to a VM on a specified controller
function New-RawHardDisk{
	param($vm, $DeviceName, $DiskType, $controller, $unitnumber, $capacity)

	$vmMo = $vm | Get-View
	$spec = New-Object VMware.Vim.VirtualMachineConfigSpec
	$chg = New-Object VMware.Vim.VirtualDeviceConfigSpec
	$chg.operation = "add"
	$chg.fileoperation = "create"
	$dev = New-Object VMware.Vim.VirtualDisk
	$dev.CapacityInKB = $capacity
	$dev.Key = - 100
	$back = New-Object VMware.Vim.VirtualDiskRawDiskMappingVer1BackingInfo
	$back.deviceName = $devicename
	if($DiskType -eq "RawPhysical"){
		$back.compatibilityMode = "physicalMode"
	}
	else{
		$back.compatibilityMode = "virtualMode"
	}
	$back.FileName = ""
	$dev.Backing = $back
	$dev.ControllerKey = $controller
	$dev.UnitNumber = $unitnumber
	$chg.device = $dev
	$spec.deviceChange += $chg
	$taskMoRef = $vmMo.ReconfigVM_Task($spec)
	$task = Get-View $taskMoRef
	while("running","queued" -contains $task.Info.State){
		$task.UpdateViewData("Info.State")
	}
	$task.UpdateViewData("Info.Result")
}

# Remove a RDM disk from a VM and optionally delete the backing file
filter remove-HD {
	param($Delete)
	$HDname = $_.Name
	$vm = Get-View -Id $_.ParentId
	# Get device key for the hard disk
	foreach($dev in $vm.Config.Hardware.Device){
		if ($dev.DeviceInfo.Label -eq $HDname){
			continue
		}
	}
	$spec = New-Object VMware.Vim.VirtualMachineConfigSpec
	$spec.deviceChange = @()
	$spec.deviceChange += New-Object VMware.Vim.VirtualDeviceConfigSpec
	$spec.deviceChange[0].device = New-Object VMware.Vim.VirtualDevice
	$spec.deviceChange[0].device.key = $dev.Key
	$spec.deviceChange[0].device.unitnumber = $dev.UnitNumber
	$spec.deviceChange[0].operation = "remove"
	$taskMoRef = $vm.ReconfigVM_Task($spec)
	$task = Get-View $taskMoRef
	while("running","queued" -contains $task.Info.State){
		$task.UpdateViewData("Info.State")
	}
	$task.UpdateViewData("Info.Result")

# Remove hard disk files (backing) from datastore
	if ($Delete){
		$fileMgr = Get-View (Get-View ServiceInstance).Content.fileManager
		$datacenter = (Get-View (Get-VM $vm.name | Get-Datacenter).ID).get_MoRef()
		foreach($disk in $vm.LayoutEx.Disk){
			if($disk.Key -eq $dev.Key){
				foreach($chain in $disk.Chain){
					foreach($fileKey in $chain.FileKey){
						$name = $vm.LayoutEx.File[$fileKey].Name
						$taskMoRef = $fileMgr.DeleteDatastoreFile_Task($name, $datacenter)
						$task = Get-View $taskMoRef
						while("running","queued" -contains $task.Info.State){
							$task.UpdateViewData("Info.State")
						}
						$task.UpdateViewData("Info.Result")
					}
				}
				continue
			}
		}
	}
}

# Main
$report = @()

# Report on all the VMs that have a RDM
$vms = Get-View -ViewType VirtualMachine
foreach($vm in $vms){
	foreach($dev in $vm.Config.Hardware.Device){
		if(($dev.gettype()).Name -eq "VirtualDisk"){
			if(($dev.Backing.CompatibilityMode -eq "physicalMode") -or
			($dev.Backing.CompatibilityMode -eq "virtualMode")){
				$esx = Get-View $vm.Runtime.Host
				$lun = $esx.Config.StorageDevice.ScsiLun | where {$_.Uuid -eq $dev.Backing.LunUuid}
				$report += New-Object PSObject -Property @{
					VMName = $vm.Name
					VMHost = ($esx).Name
					HDLabel = $dev.DeviceInfo.Label
					HDDeviceName = $dev.Backing.DeviceName
					HDFileName = $dev.Backing.FileName
					HDMode = $dev.Backing.CompatibilityMode
					HDSize = $dev.CapacityInKB
					LunDisplayName = $lun.DisplayName
					HDCtrlType = ($vm.Config.Hardware.Device | where {$_.Key -eq $dev.ControllerKey}).GetType().Name
					HDController = $dev.ControllerKey
					HDUnit = $dev.UnitNumber
					HDDiskMode = $dev.Backing.DiskMode
					LunCanonical = $lun.CanonicalName
					LunDeviceName = $lun.DeviceName
				}
			}
		}
	}
}
$report | Export-Csv "C:\VM-with-RDM.csv" -NoTypeInformation -UseCulture

$report | Group-Object -Property VMName | % {
	$vm = Get-VM $_.Name
# Stop the VM
	Write-Host "Stop VM" $_.Name
	$VM | Get-VMGuest | where {$_.State -eq "Running"} | Shutdown-VMGuest - Confirm:$false
# Remove the RDM disk(s)
	$_.Group | % {
		Write-Host "`tremove HD" $_.HDLabel
		$vm | Get-HardDisk -DiskType ("Raw" + $_.HDMode.TrimEnd("Mode")) | Remove-HD - Delete:$true
	}
# vMotion the VM
	Write-Host "Moving VM"
	$newvm = $vm | Move-VM -Destination (Get-VMHost -Name $tgtESX)
# Attach the RDM disk(s) back
	$_.Group | % {
		Write-Host "`tAdd HD" $_.HDLabel
		New-RawHardDisk -Vm $newvm -DiskType ("Raw" + $_.HDMode.TrimEnd("Mode")) -DeviceName $_.LunDeviceName -Controller $_.HDController -UnitNumber $_.HDUnit -Capacity $_.HDSize
	}
# Power on the VM
	Write-Host "Start VM" $_.Name
	$newvm | Start-VM - Confirm:$false
}

Line 2: destination ESX server

Line 18-23: support for physical and virtual mode RDM

Line 118: dump the RDM info to a CSV file

Line 120-141: this is the part where the RDM disk(s) are removed, the VM vMotioned and the RDM disk(s) re-attached.

Line 136: because a guest can have more than one RDM I use the Group-Object cmdlet