Set-ClusterVMAntiAffinity.ps1

function Set-ClusterVMAntiAffinity {
    <#
        .SYNOPSIS
        Will configure Preferred Owners for Virtual Machine running on Failover Cluster
    
        .DESCRIPTION
        Uses Invoke-Command to allow for PSCredential
        If Preferred Owner is provided will verify if it matches cluster Owner Nodes. 
        If yes - will set Preferred Owners for given VMs.
        If no - will abort.
        If $null, or '' is provided will reset Preferred Owners to defaults for given VM
    
        .PARAMETER Cluster
        Cluster Name
    
        .PARAMETER Credential
        Optional PSCredential used to connect to cluster
    
        .PARAMETER VMName
        Virtual Machine Name or array of names to process
    
        .PARAMETER AntiAffinityGroupName
        AntiAffinity Group name to configure VM with.

        .PARAMETER Append
        Switch option whether group should be added to current set.
    
        .EXAMPLE
        Set two VMs 'windows2016' and 'windows2016core' with AntiAffinity Group named 'templates'

        Set-ClusterVMAntiAffinity -Cluster 'cluster0'  -VMName 'windows2016','windows2016core' -AntiAffinityGroupName 'Templates' -Verbose
        VERBOSE: Processing with default credentials of user {mczerniawski_admin}
        VERBOSE: Processing VM {windows2016}
        VERBOSE: VM {windows2016} current AntiAffinity Groups: {}
        VERBOSE: Setting Anti Affinity:  {Templates} for VM {windows2016} 

        VERBOSE: Processing VM {windows2016core}
        VERBOSE: VM {windows2016core} current AntiAffinity Groups: {Template}
        VERBOSE: Setting Anti Affinity:  {Templates} for VM {windows2016core} 
        Cluster     VMName          AntiAffinityGroupName
        -------     ------          ---------------------
        cluster0 windows2016     Templates            
        cluster0 windows2016core Templates   

        .EXAMPLE
        Add AntiAffinity Group named 'templates2' to two VMs 'windows2016' and 'windows2016core'

        Set-ClusterVMAntiAffinity -Cluster 'cluster0'  -VMName 'windows2016','windows2016core' -AntiAffinityGroupName 'Templates2' -Verbose -Append
        VERBOSE: Processing with default credentials of user {mczerniawski_admin}
        VERBOSE: Processing VM {windows2016}
        VERBOSE: VM {windows2016} current AntiAffinity Groups: {Templates}
        VERBOSE: Append selected. Preparing new object for AntiAffinity Group name for VM {windows2016}.
        VERBOSE: Setting Anti Affinity:  {Templates2} for VM {windows2016} 

        VERBOSE: Processing VM {windows2016core}
        VERBOSE: VM {windows2016core} current AntiAffinity Groups: {Templates}
        VERBOSE: Append selected. Preparing new object for AntiAffinity Group name for VM {windows2016core}.
        VERBOSE: Setting Anti Affinity:  {Templates2} for VM {windows2016core} 
        Cluster     VMName          AntiAffinityGroupName  
        -------     ------          ---------------------  
        cluster0 windows2016     {Templates, Templates2}
        cluster0 windows2016core {Templates, Templates2}

        .EXAMPLE
        Clear any Anti Affinity Group name on 'windows2016' VM

        Set-ClusterVMAntiAffinity -Cluster 'cluster0'  -VMName 'windows2016' -AntiAffinityGroupName $null -Verbose
        VERBOSE: Processing with default credentials of user {mczerniawski_admin}
        VERBOSE: Provided no AntiAffinity Group Name. Will reset to default setting
        VERBOSE: Processing VM {windows2016}
        VERBOSE: VM {windows2016} current AntiAffinity Groups: {}
        VERBOSE: Setting Anti Affinity:  {} for VM {windows2016} 

        Cluster     VMName      AntiAffinityGroupName
        -------     ------      ---------------------
        cluster0 windows2016     
        
    #>
    
    [CmdletBinding()]
    param(
        [Parameter(Mandatory, HelpMessage = 'Provide Cluster Name',
            ValueFromPipeline, ValueFromPipelineByPropertyName)]
        [ValidateNotNullOrEmpty()]
        [System.String]
        $Cluster,
    
        [Parameter(Mandatory = $false, HelpMessage = 'Provide Credentials for Cluster',
            ValueFromPipeline, ValueFromPipelineByPropertyName)]
        [System.Management.Automation.PSCredential]
        $Credential,
    
        [Parameter(Mandatory, HelpMessage = 'Provide VMName',
            ValueFromPipeline, ValueFromPipelineByPropertyName)]
        [ValidateNotNullOrEmpty()]
        [System.String[]]
        $VMName,
    
        [Parameter(Mandatory = $false, HelpMessage = 'Provide Preferred Owners Nodes to restrict VM to failover to',
            ValueFromPipeline, ValueFromPipelineByPropertyName)]
        [System.String[]]
        $AntiAffinityGroupName,

        [Parameter(Mandatory = $false, HelpMessage = 'Append AntiAffinity group to current set',
            ValueFromPipeline, ValueFromPipelineByPropertyName)]
        [switch]
        $Append
    )
    begin {
        #region PSSession parameters
        $connectionParams = @{
            ComputerName = $Cluster
        }
        if ($PSBoundParameters.ContainsKey('Credential')) {
            $connectionParams.Credential = $Credential
            Write-Verbose -Message "Processing with provided credentials {$($Credential.UserName)}"
        }
        else {
            Write-Verbose -Message "Processing with default credentials of user {$($env:USERNAME)}"
        }
        $ClusterSession = New-PSSession @connectionParams -ErrorAction Stop
        #endregion 
         
        #null or empty string - reset to defaults
        if (-not $AntiAffinityGroupName) {
            Write-Verbose -Message "Provided no AntiAffinity Group Name. Will reset to default setting"
            $AntiAffinityGroupName = ''
        }
    }
    process {
        foreach ($VM in $VMName) {
            Write-Verbose -Message "Processing VM {$VM}"
            $ClusterVM = Invoke-Command -Session $ClusterSession  -ScriptBlock {
                Get-ClusterGroup -Name $USING:VM -ErrorAction SilentlyContinue 
            }
            if (-not $ClusterVM) { 
                Write-Error -Message "VM {$VM} not found on cluster {$Cluster}"
            }
            else {
                Write-Verbose -Message "VM {$VM} current AntiAffinity Groups: {$($ClusterVM.AntiAffinityClassNames)}"
                #set to defaults
                if ($Append) {
                    Write-Verbose -Message "Append selected. Preparing new object for AntiAffinity Group name for VM {$VM}."
                    $finalAntiAffinityGroupName = @($ClusterVM.AntiAffinityClassNames) + @($AntiAffinityGroupName)
                }
                else {
                    $finalAntiAffinityGroupName = @($AntiAffinityGroupName)
                }
                Write-Verbose -Message "Setting Anti Affinity:  {$AntiAffinityGroupName} for VM {$VM} "
                $finalVMAntiAffinity = Invoke-Command -Session $ClusterSession  -ScriptBlock {
                    (Get-ClusterGroup -Name $USING:VM).AntiAffinityClassNames = @($USING:finalAntiAffinityGroupName)
                    (Get-ClusterGroup -Name $USING:VM).AntiAffinityClassNames
                }
                [pscustomobject]@{
                    Cluster               = $Cluster
                    VMName                = $VM
                    AntiAffinityGroupName = $finalVMAntiAffinity
                }
            }
        }
    }
    end {
        $ClusterSession | Remove-PSSession -ErrorAction SilentlyContinue
    }
}