Automation

Hi everyone,

I got this fuction from LucD in another forum post and modified it to attempt to convert a large number of VMs from thick to thin disks.  I seem to be getting an error on the first VM every time and the second seems to be working fine.  If someone could point out what I've done wrong I would appreciate it.

Error:

You cannot call a method on a null-valued expression.
At C:\Users\xxx\Documents\xxx.ps1:33 char:31
+             $vmView.RelocateVM <<<< ($spec, $null)
    + CategoryInfo          : InvalidOperation: (RelocateVM:String) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

Script:

$vmarray = @("TestVM1","TestVM2")
$datastore = Get-Datastore | Sort FreeSpaceMB -Descending
    function Move-VMThin {
        PARAM(
             [Parameter(Mandatory=$true,ValueFromPipeline=$true,HelpMessage="Virtual Machine Objects to Migrate")]
             [ValidateNotNullOrEmpty()]
                [System.String]$VM
            ,[Parameter(Mandatory=$true,HelpMessage="Destination Datastore")]
             [ValidateNotNullOrEmpty()]
                [System.String]$Datastore
        )
      
            Begin {
            #Nothing Necessary to process
            } #Begin
      
        Process {       
            #Prepare Migration info, uses .NET API to specify a transformation to thin disk
            $vmView = Get-View -ViewType VirtualMachine -Filter @{"Name" = "$VM"}
            $dsView = Get-View -ViewType Datastore -Filter @{"Name" = "$Datastore"}
          
            #Abort Migration if free space on destination datastore is less than 50GB
            if (($dsView.info.freespace / 1GB) -lt 50) {throw "Move-ThinVM ERROR: Destination Datastore $Datastore has less than 50GB of free space. This script requires at least 50GB of free space for safety. Please free up space or use the VMWare Client to perform this Migration"}
    
            #Prepare VM Relocation Specificatoin
            $spec = New-Object VMware.Vim.VirtualMachineRelocateSpec
            $spec.datastore =  $dsView.MoRef
            $spec.transform = "sparse"
          
            #Perform Migration
            $vmView.RelocateVM($spec, $null)
        } #Process
    }
for ($i=0; $i -lt $vmarray.count; $i++)
{
$datastore
$snapshot = Get-VM -Name $vmarray[$i] | Get-Snapshot
if ($snapshot -eq $null)
{
  $vmds = Get-VM -Name $vmarray[$i] | Get-Datastore
  if ($vmds -ne $datastore[0])
  {
   Move-VMThin -VM $vmarray[$i] -Datastore $datastore[0]
  }
  if ($vmds -eq $datastore[0])
  {
   Move-VMThin -VM $vmarray[$i] -Datastore $datastore[1]
  }
}
if ($snapshot -ne $null)
{
  Write-Host $vmarray[$i]+"has a Snapshot" -ForegroundColor Red
}
}

Could it be that the first VM has files on more than 1 datastore ?

Does

Get-VM -Name TestVM1 | Get-Datastore

return more than 1 datastore ?

LucD,

No, it only has files on one datastore.

Do your datastores have similar names.

What I mean, the Get-View in the function uses a filter where it retrieves the datastore based on it's name.

If you have datastores that start with the same characters, it can be that more than 1 object is returned.

For example: the datastores are called "ds1" and "ds11".

Get-View -ViewType Datastore -Filter @{"Name"="ds1"}

will return both.

LucD,

Thanks for you quick responses.  I am testing this in my lab at the moment where all my datastores have radically different names.  When I am able to get this error worked out and I move the script into production the datastores will all have similar names.  I think I have midigated this issue with the following commands.

$datastore = Get-Datastore | Sort FreeSpaceMB -Descending
Move-VMThin -VM $vmarray[$i] -Datastore $datastore[0] or Move-VMThin -VM $vmarray[$i] -Datastore $datastore[1]

I don't think this should be an issue there either since all datastores end in a unique 2 digit number.

Perhaps I am just using the funciton incorrectly, but then I don't understand why some VMs error out and others don't.

I may have found the issue.  It seems I have duplicated a variable that is used in the function.  I have modified my script and I am testing it out now.

Nevermind, no change.

There must be something failing with the Get-View cmdlet.

Can you dump the $dsView variable to the console ?

Just add a line in the function like this

...

$dsView = Get-View -ViewType Datastore -Filter @{"Name" = "$Datastore"}
$dsView

...

Info                : VMware.Vim.VmfsDatastoreInfo
Summary             : VMware.Vim.DatastoreSummary
Host                : {HostSystem-host-15602, HostSystem-host-17697, HostSystem-host-18280, HostSystem-host-18661...}
Vm                  : {VirtualMachine-vm-15756, VirtualMachine-vm-15758, VirtualMachine-vm-18849, VirtualMachine-vm-19074...}
Browser             : HostDatastoreBrowser-datastoreBrowser-datastore-15643
Capability          : VMware.Vim.DatastoreCapability
IormConfiguration   : VMware.Vim.StorageIORMInfo
Parent              : Folder-group-s5
CustomValue         : {}
OverallStatus       : green
ConfigStatus        : gray
ConfigIssue         : {}
EffectiveRole       : {-1}
Permission          : {}
Name                : xxx
DisabledMethod      : {}
RecentTask          : {}
DeclaredAlarmState  : {alarm-41.datastore-15643, alarm-51.datastore-15643, alarm-9.datastore-15643}
TriggeredAlarmState : {}
AlarmActionsEnabled : True
Tag                 : {}
Value               : {}
AvailableField      : {}
MoRef               : Datastore-datastore-15643
Client              : VMware.Vim.VimClient

You cannot call a method on a null-valued expression.
At C:\Users\xxx\Documents\xxx.ps1:32 char:31
+             $vmView.RelocateVM <<<< ($spec, $null)
    + CategoryInfo          : InvalidOperation: (RelocateVM:String) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

The issue seems to fall on $vmView rather than $dsView.  It appears the $vmView is empty for the VM I'm trying to move.  Any suggestions?

I changed:

$vmView = Get-View -ViewType VirtualMachine -Filter @{"Name" = "$VM"}

to
$vmView = Get-VM -Name "$VM" | Get-View

It now appears to work.  I'm not sure what the difference is though.

LucD,

Thanks for pointing me in the right direction.  I purchased your book the other week and I have found it to be a valuable asset.

Hosted

Thanks, and great you find the book useful.

Does this return anyhting at all ?

Get-View -ViewType VirtualMachine -Filter @{"Name" = "TestVM1"}

Get-View -ViewType VirtualMachine -Filter @{"Name" = "TestVM1"} returns nothing.

And this does return the guest ?

Get-VM -Name "TestVM1"

Yes,

Get-VM -Name "TestVM1"

and

Get-VM -Name "TestVM1" | get-view

both work, but

Get-View -ViewType VirtualMachine -Filter @{"Name" = "TestVM1"}

does not.

Very strange, can't reproduce this.

For the fun of it, can you try

Get-View -ViewType VirtualMachine -Filter @{"Name"=(Get-VM TestVM1).Name}

I agree, it is strange.  Nothing is returned from that command either.

If it's not confidential, can you include the output from

Get-VM TestVM1 | Get-View

The mystery is solved, the actual name of the VM contained some RegEx meta-characters.

When these were escaped with the back-slash, the Get-View filter worked without a problem.

For example, the VM name contains parenthesis, which are RegEx grouping characters. This

$vmName = "TestVM(1)"

Get-View -ViewType VirtualMachine -Filter @{"Name"=$vmName}

will not return anything.

But

$vmName = "TestVM\(1\)"

Get-View -ViewType VirtualMachine -Filter @{"Name"=$vmName}

will.

Advice: avoid RegEx meta-characters in the name of your VMs.

LucD,

Thank for all your help.

One thing I find interesting is that the Get-VM cmdlet seems to be able to handle RegEx data in the virtual machine name.  So, if you needed a script that was more flexible, but less efficient you could use the following.

$vmName = "TestVM(1)"

Get-VM $vmName | Get-View

I realize that Get-View -ViewType VirtualMachine -Filter @{"Name"=$vmName} seems to be the almost universally excepted way to perform this operation, and in my quick testing this command took roughly 1 second less to complete.  However, when taken in the context of a script whose primary function is to storage vMotion one or many virtual machines, the difference becomes negligible.

If the script's primary function is to gather information though, I could see how the efficient command would be highly preferred over the flexible command since running the commands 1000 times would yield a 16.6 minute difference.  A time difference that is hardly negligible.

Hosted

The Get-VM cmdlet offers very limited name masking capabilities compared to the Get-View filter.

And the Get-View cmdlet is, as you noticed, way faster in a medium to big environment. When you also use the Property parameter it is even faster.

In the end it isn't too difficult to copy with all the RegEx meta-characters when needed.

The Replace method is one way how to tackle these meta-characters.

Now I'm interested in being able to remove all RegEx metacharacters from a given string.  Is there a simple catch-all or would every string have to be something like:

Get-View -ViewType VirtualMachine -Filter @{"Name"="$vmName".Replace('(','\(').Replace(')','\)').Replace(']','\]').Replace('[','\[').Replace('^','\^').Replace('\','\\').Replace('.','\.').Replace('|','\|').Replace('?','\?').Replace('+','\+').Replace('*','\*').Replace('$','\$')}

Did I even get them all?  I knew I should have taken a programming class in college.

Hosted

Turns out there is a much more elegant and simpler solution.

The RegEx object has a method, called Escape, that does it all for you.

Get-View -ViewType VirtualMachine -Filter @{"Name"=[regex]::Escape($vmName)}

I'm going to start using this everytime I use a Get-View with a filter that uses a string :smileyhappy: