Migrating VMs from ESX4 to ESX5

One of my customers asked me to help them migrate their VMs from an ESX 4 environment into a brand new ESX 5 environment.  This new environment had brand new servers and storage (as well as fibre switches); they needed a forklift.  We discussed migration strategies (presenting some shared storage to both environments, etc.) but, due to a long list of very environment specific considerations, we determined that cold migrations during outage windows would be the best solution.

As such, there was a fair amount of hands on work that would be required.  Given that a large amount of the work would need to be done after hours, automation became a high priority.  To that end, I put together a PowerCLI script that the migration team could use to perform these migrations.  This script is designed to be used by an administrator who can babysit the process, for it spits out its status updates and end results so that the administrator can validate the important settings.

Using the script dramatically sped up the process, so I figured that I'd go ahead and post it here in case it can help anyone else in a similar situation.  As always, this script is provided as is and there are no guarantees implied.  While it worked in this particular situation, you should verify that it works as intended in your environment before you try to use this script.

#Migrates 1 VM from a vSphere 4 environment into a vSphere 5 environment, performing most of the necessary upgrades for you.
#$VMString should be the name of the VM that you wish to migrate; wildcards are acceptable but it can only resolve to a single VM.
#$DestDSString is the name of the datastores that the script will choose from; it will select the datastore with the most free space from all datastores that match this naming pattern.
#$DestHostString should be the name of an ESX 5 host in the new environment with access to the desired storage
#$dataCenterString should be the name of the virtual datacenter in which the VM will reside
#$DSFreeSpace is an integer representing the % free space desired on the datastore after the VM is moved onto it; aborts if there is not enough space
param
(
   $VMString = (Read-Host("VM Name")),
   $DestDSString = (Read-Host("Destination Datastore")),
   $DestHostString = (Read-Host("Destination Host")),
   $dataCenterString = (Read-Host("Datacenter")),
   $DSFreeSpace = 20
)

$thisVM = Get-VM $VMString
if ($thisVM.Count -gt 1)
{
   echo "Too many VMs found that match string $VMString!"
   exit
}
if ((get-vm -name $VMString).ExtensionData.GuestHeartbeatStatus -eq "gray")
{
   echo "VM Tools not running, aborting script."
   exit
}
$destDS = (Get-Datacenter -name $dataCenterString | get-datastore -name $DestDSString | sort "freespacegb" -Descending)[0]
if ((($destDS.FreeSpaceGB - $thisVM.usedspaceGB) / $destDS.CapacityGB * 100) -lt $DSFreeSpace)
{
   echo "Destination Datastore $($destDS.name) will have less than $DSFreeSpace% free space. Aborting migration."
   exit
}
$destHost = get-vmhost $DestHostString
echo "$thisVM current datastore: $($thisVM.DatastoreIDList)"
echo "$thisVM current network: $($thisVM.NetworkAdapters.NetworkName)"
echo "Shutting down $($thisVM.Name) for cold migration."
$thisVM | Shutdown-VMGuest -Confirm:$false
do
{
   echo "Waiting for shutdown to complete..."
   Start-Sleep -Seconds 15
} while ((get-vm -name $VMString).powerstate -eq "PoweredOn")
echo "Moving $thisVM to $destHost on $destDS"
Move-VM -VM $thisVM -Destination $destHost -datastore $destDS -DiskStorageFormat Thin | out-Null
$thisVM | New-Snapshot -Name "Pre-Upgrade" | out-Null
echo "Starting up $($thisVM.Name) for VMTools update."
$thisVM | Start-VM | out-Null
do
{
   echo "Waiting for startup to complete..."
   Start-Sleep -Seconds 15
} while ((get-vm -name $VMString).ExtensionData.GuestHeartbeatStatus -eq "gray")
Start-Sleep -Seconds 15
echo "Updating VMTools..."
$thisVM | Update-Tools | out-Null
Start-Sleep -Seconds 60
do
{
   echo "Waiting for startup to complete..."
   Start-Sleep -Seconds 15
} while ((get-vm -name $VMString).ExtensionData.GuestHeartbeatStatus -eq "gray")
echo "Shutting down $($thisVM.Name) for VM Hardware Version Update."
$thisVM | Shutdown-VMGuest -Confirm:$false
do
{
   echo "Waiting for shutdown to complete..."
   Start-Sleep -Seconds 15
} while ((get-vm -name $VMString).powerstate -eq "PoweredOn")
echo "Updating VM Hardware"
Set-VM -VM $thisVM -Version v9 -Confirm:$false

echo "-----"
echo "$($thisVM.Name)" 
echo ""
echo "VMTools version: $($thisVM.ExtensionData.Config.tools.ToolsVersion)"
echo "VM Hardware version: $((get-vm -name $VMString).version)"
echo "VM is on $($thisVM.DatastoreIdList.count) datastores."
echo "-----"