A few days ago, Ben Armstrong, the Virtual PC Guy posted on his blog the following:
Why would you backup VMs / When / What’s the best practice
Why? Just in case of a disaster, you should be able to recover your VMs.
When? The best practive analyzer has the answer:
Get-BpaModel -ModelId Microsoft/Windows/Hyper-V | Invoke-BpaModel
Get-BpaModel | ? Name -match "Hyper-V" |
Get-BpaResult | ?{($_.Resolution) -and ($_.Severity -eq "Error")}|
fl -p ResultNumber,Severity,Category,Title,Problem,Resolution
How do I perform the backup with PowerShell
- Prerequisite #1: Install the backup features
Get-WindowsFeature | ? { $_.DisplayName -match "Backup" }
Add-WindowsFeature -Name Windows-Server-Backup -IncludeAllSubFeature:$true -Restart:$false
Prerequisite #2: Make sure the integration services have been installed
Get-VM | ? State -eq "Running" |
Select Name,State,Integrationservicesversion |
ft -AutoSize
Query the VM integration services version of running VMs to prevent them going into a saved state if they don’t have the latest VM integration services installed.
Ben Armstrong, the Virtual PC Guy in his posts also said:
The virtual machine will only be put into a saved state if it is not running the latest virtual machine additions (or is not a Windows virtual machine).
More info about VM integration services, see my post: https://p0w3rsh3ll.wordpress.com/2012/11/15/follow-up-about-hyper-v-vm-integration-services/
Check what VM can be backed up and how
Get-WBVirtualMachine | ft VMName,Caption -AutoSize
If the VM is off, the backup is performed from the saved state.
If the VM is running, the backup is performed using a snapshot.
Backup a single VM manually and synchronously
# Create an empty policy object
$pol = New-WBPolicy
# Add a single VM to the backup
Get-WBVirtualMachine | ? VMName -eq myVMName | Add-WBVirtualMachine -Policy $pol
# Define a target folder for the backup
$targetvol = New-WBBackupTarget -NetworkPath \\mytargetserver.fqdn\HVBackup$ -Credential (Get-Credential) -NonInheritAcl:$false -Verbose
Add-WBBackupTarget -Policy $pol -Target $targetvol
# Define a schedule
Set-WBSchedule -Policy $pol -Schedule ([datetime]::Now.AddMinutes(10))
# Start the backup synchronously
Start-WBBackup -Policy $pol
Note that you cannot start a saved VM (off) when there’s a backup in progress: 
# Review the result
Get-WBSummary
Get-WBBackupSet -BackupTarget (Get-WBBackupTarget $pol)
Get-WBJob -Previous 1
We have the ability to add multiple VMs to a single backup job. However VMs will be backed up sequentially.
You may have also seen how tedious it can be to perform the recovery in Ben Armstrong’s blog post, so I propose the following code snippet that may help:
$BackupShare = "\\mytargetserver.fqdn\HVBackup$"
$cred = (Get-Credential)
Get-VM | ForEach-Object -Process {
$targetfolder = Join-Path -Path $BackupShare -ChildPath "$($env:COMPUTERNAME)\$($_.Name)"
If (Test-Path $targetfolder) {
Write-Verbose -Message "Previous backup for VM $($_.Name) found" -Verbose
# Delete it first
try {
Remove-Item -Path $targetfolder -Force -ErrorAction Stop
} catch {
Write-Warning -Message "Failed to remove target folder $targetfolder"
return
}
# Create directory
try {
New-Item -Path $targetfolder -ItemType Directory -ErrorAction Stop
} catch {
Write-Warning -Message "Failed to create target folder $targetfolder"
return
}
} else {
# Create directory
try {
New-Item -Path $targetfolder -ItemType Directory -ErrorAction Stop
} catch {
Write-Warning -Message "Failed to create target folder $targetfolder"
return
}
}
# Create an empty policy object
$pol = New-WBPolicy
# Add the VM
Get-WBVirtualMachine | ? VMName -eq $_.Name | Add-WBVirtualMachine -Policy $pol
# Define a target folder
$targetvol = New-WBBackupTarget -NetworkPath $targetfolder -Credential $cred -NonInheritAcl:$false -Verbose
Add-WBBackupTarget -Policy $pol -Target $targetvol
# Set a schedule
Set-WBSchedule -Policy $pol -Schedule ([datetime]::Now.AddMinutes(10))
# Start the backup
Start-WBBackup -Policy $pol -Async
# Let us know the status of the running job
While((Get-WBJob).JobState -eq "Running") {
$percent = ([int](@(([regex]'.*\((?<percent>\d{2})\%\).*').Matches((Get-WBJob).CurrentOperation).Groups)[-1].Value))
if ($percent) {
Write-Progress -Activity "Backup of VM $($_.Name) in progress" -Status "Percent completed: " -PercentComplete $percent
} else {
Write-Progress -Activity "Backup of VM $($_.Name) in progress" -Status (Get-WBJob).CurrentOperation
}
}
}
>_ 