Thursday, December 15, 2011

Making VMs highly available with PowerShell

If you have been following you will know that I have a bunch of copies of a MasterVM.

These were created using Export / Import so they are all nice and tidy in their own folders on the same volume.  If your target volume was a CSV (Cluster Shared Volume) then you are all set for this one and are ready for a multi-node cluster.  If your destination was not a CSV, but possibly another local volume, you can still make your VMs Highly Available, but you won’t be able to migrate.  This is fine for testing, but not really of high value in production.

Here is the script:

if ($highlyAvailable -match "yes") {
    write-progress -Id 1 "Making each VM highly available" -Status "Executing"
    # Make a remote session here to run the below loop passing in $arrUpdatedVms
    $session = New-PSSession -computerName $hypervHost
    Invoke-Command -scriptblock { Import-Module FailoverClusters } -session $session
    Import-PSSession -module FailoverClusters -session $session
    foreach($e in $arrUpdatedVms){
        $vm = $e.Split(",")
        $deviceName = $vm[0]
        Add-ClusterVirtualMachineRole -VirtualMachine $deviceName
    write-progress -Id 1 "Making each VM highly available" -Completed $TRUE

The most interesting thing that I do here is that I am using Import-PSSession to bring the Clustering cmdlets (installed on the remote Hyper-V server) into my local script execution session.  This allows me to use the cmdlets as if they were installed locally, but without installing them.  This is pretty useful.

The hitch is that your networking cannot incur any blips.  Your session must remain solid or the script simply begins to fail.

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