Expanding upon the basics demonstrated in Part I of this series, let’s now look at exporting multiple machines using a single PowerShell script.  We’ll use the same director structure as outlined in Part I, but here we have a few additional challenges to overcome.

• Selecting the Virtual Machines to export.
• Ensuring that we only export one at a time to reduce the disk I/O and resulting disk fragmentation that will occur if simply try to export all of the machines at one time.
• You want to export the machines while they’re in a running state.

The following PowerShell script will do the job admirably, but let’s take a look at a few key sections that make this possible.

First the assumptions:

• HyperV Host is running Windows Server 2012 R2 as this will not work on Windows Server 2012.

Then the script:

#

# $RootPath: Can be changed to point where you’d like the Virtual Machines exported and can be any valid

#            drive path.

$RootPath = ‘E:\Exports-RONBOKEVGA1\Backup\’

# $OutputDate: Is simply used to create a unique folder name that later can have it’s CreationDate checked

#              for deletion later.

$OutputDate = (Get-Date).Year.ToString() + ‘.’ + (Get-Date).Month.ToString() + ‘.’ + (Get-Date).Day.ToString() + ‘.’ + (Get-Date).Hour.ToString() + ‘.’ + (Get-Date).Minute.ToString() + ‘.’ + (Get-Date).Second.ToString()

#Clean up old Export-VM folders older than one month ago to reduce disk space consumption.

foreach ($i in Get-ChildItem $RootPath)

{

    if ($i.CreationTime -lt ($(Get-Date).AddMonths(-1)))

        {

            #Write-Output $i.Name.ToString()

            Remove-Item $i.PSPath -Recurse

        }

}

#Create new Export folder with current date/time.

$ExportPath = New-Item ($RootPath + ‘ ‘ + $OutputDate) -type directory

# Set the $Status variable to a default value which should indicate that no VM’s are being exported.

$Status = Get-VM | Where Status -EQ ‘Exporting virtual machine’

Function CheckStatus()

{

    Do

    {

        # We only want to be exporting one VM at a time so that we don’t overtax disk I/O.

        # The function ensures that by checking the VM status before starting the next export.

        Start-Sleep -s 60

        $Status = Get-VM | Where Status -EQ ‘Exporting virtual machine’

        $d = Get-Date -DisplayHint Time

        Write-Host “Exporting…” $d -ForegroundColor Yellow

    } While ($Status.Count -ne 0)

  }

Function ExportVM($VM)

{

    Export-VM -ComputerName $env:COMPUTERNAME -Name $VM.VMName -Path $ExportPath -AsJob

    Write-Host ‘Starting Export: ‘ $VM.VMName -ForegroundColor Yellow

}

# This is our list of VM’s to export based on a naming filter.

# It’s important to be consistent when naming VM’s in the Hyper-V Console!

$VMList =  Get-VM | Where-Object {$_.Name -like ‘RonBok*’}

Write-Host $VMList.VMName

Clear-Host

ForEach ($VM in $VMList)

{

    # The DPM VM’s are using physical disks, so they cannot be exported.

    # They’d be so large that it would be impossible anyway.

    If (($VM.VMName -ne ‘RonBokDPM1’) -and ($VM.VMName -ne ‘RonBokDPM2’))

    {

        ExportVM $VM

        CheckStatus

    }

}

The key to this whole thing are the two functions ExportVM() and CheckStatus().  CheckStatus() queries the list of VM’s in HyperV and looks for any VM that has a status of ‘Exporting virtual machine’.  It’s rather fragile in that respect, but it works.

The other thing to note is the ForEach loop at the bottom … really the main part of the script.  It creates an object $VMList of all the VM’s in my environment that begin with ‘RonBok*’ as those are the ones I want exported.  For your environment you’ll need to decide what kind of query works best for you and change the script accordingly.  Also note that I have a few System Center Data Protection Manager 2012 R2 machines in this list an want them excluded.  Those VM’s I can’t export anyway because they are using physical disks for storage.  I’ll cover System Center Data Protection Manager 2012 R2 in Part III.

If you have any questions feel free to post in the comments.

Have fun!

After spending many hours building out multiple Hyper-V guests there’s always a chance that something will go wrong and you’ll be needing a backup to restore from.  There are many options available, but suffice it to say that while useful, Checkpoints & Replication are not backups.

So what are the other options?  The simplest is an Hyper-V Export to another location.  The more robust solution is using System Center 2012 R2 Data Protection Manager, [which I’ll begin to cover in Part III].

Now, while we can manually Export… any guest from Hyper-V Manager wouldn’t it be nice to be able to query the list of machines and then Export… them one by one to a location on an automated basis using Task Scheduler?

Before we get into the PowerShell to accomplish this task, I’d like to point out that Microsoft still has not provided an –Overwrite switch on the Export-VM command.  Thus if you want to repeat this process and keep multiple weeks or a months backups you’ll have to find another option for if the files/folders exist the Export-VM command will fail to execute.  So what’s a possible solution?  Create a folder with a current data/time stamp to hold all of the exported machines and then do this each time the PowerShell command executes.  Simple right?  Well, keep in mind that after awhile these folders will pile up and you’ll also need a method of deleting old ones as well depending upon how long you want to store them. 

In the example above a separate drive D: has been designated as the Export location and a folder called Exports has been created to store each export based upon the data/time the Task Scheduler task executes the PowerShell script.

The first step in the PowerShell script is to query the list of existing folders and then removes the folder older than one month from the current date/time.  This keeps 5 backups and helps reduce the disk space required for the backups.  [NOTE:  System Center 2012 R2 Data Protection Manager can significantly reduce backup disk space consumption, but we’ll cover that in Part III.]

So let’s look at a simple script to accomplish the above, with a single machine, then we’ll get fancy (in Part II) skirting some other issues that result from exporting multiple machines at one time and the disk I/O, we’ll also address the SLA issue of 99.9% availability for the machines you want to backup, etc.

First the assumptions:

• We have only one guest machine we want to export/backup.
• It is OK to stop the guest machine while we back it up and then we’ll restart it after the export is complete.
• It only takes 3 minutes to shutdown the guest machine properly.

The simple PowerShell script below will accomplish this task given the assumptions above.

#

# $RootPath: Can be changed to point where you’d like the Virtual Machines exported and can be any valid

#            drive path.

$RootPath = ‘D:\Exports\’

# $OutputDate: Is simply used to create a unique folder name that later can have it’s CreationDate checked

#              for deletion later.

$OutputDate = (Get-Date).Year.ToString() + ‘.’ + (Get-Date).Month.ToString() + ‘.’ + (Get-Date).Day.ToString() + ‘.’ + (Get-Date).Hour.ToString() + ‘.’ + (Get-Date).Minute.ToString() + ‘.’ + (Get-Date).Second.ToString()

$GuestVMName = “GuestVirtualMachineName”

Try

{

    Stop-VM -Name $GuestVMName

    Start-Sleep -Seconds 180

}

Catch

{

    Break

}

#Clean up old Export-VM folders older than one month ago to reduce disk space consumption.

foreach ($i in Get-ChildItem $RootPath)

{

    if ($i.CreationTime -lt ($(Get-Date).AddMonths(-1)))

        {

            #Write-Output $i.Name.ToString()

            Remove-Item $i.PSPath -Recurse

        }

}

#Create new Export folder with current date/time.

$ExportPath = New-Item ($RootPath + ‘ ‘ + $OutputDate) -type directory

#Export the VM.

Export-VM -ComputerName $env:COMPUTERNAME -Name $GuestVMName -Path $ExportPath

#Start the VM.

Try

{

    Start-Sleep -Seconds 180

    Start-VM -Name $GuestVMName

}

Catch

{

    Break

}

Adding this PowerShell to Task Scheduler and setting up a schedule provides an easy way to backup this single guest machine on a regular basis.

In Part II of this series, we’ll get into a more real world example of how to accomplish this for multiple guests and ensure that we’re exporting only one machine at a time to ensure quality disk I/O on the destination disk.  In Part III, we’ll get into System Center 2012 R2 Data Protection Manager.