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How to configure AntiAffinityClassNames in Failover Clustering using Windows PowerShell

AntiAffinityClassNames is a cluster group property in Windows Failover Clustering used to identify cluster groups that should not be hosted on the same node. When working with clustered Hyper-V environments there is a 1:1 relationship between a cluster group and a virtual machine, and thus we can configure Anti-Affinity for virtual machines using the AntiAffinityClassNames property. For more information, see the links in the resource section in the bottom of the article.

What I want to show in this article is how to configure the AntiAffinityClassNames property using PowerShell. Most articles I have seen in regards to AntiAffinityClassNames covers how to use cluster.exe to configure the property, and since the cluster.exe was deprecated in Windows Server 2008 R2 (it`s still available as a deprecated command) it might be a good idea to learn how to configure this using the new Failover Clustering PowerShell module. In addition you also get other benefits available in PowerShell such as pipelining, export/import to/from different data sources, grouping and so on.

AntiAffinityClassNames is a property of a cluster group, but before we configure the property we need to look at what type it is. We can do this by piping the output of Get-ClusterGroup to the Get-Member cmdlet:

image

We can see in the definition of the property that it is a System.Collections.Specialized.StringCollection type. This means we can not just pass a text string as the property value, we need to create a object of the correct type. The reason this property is not just a System.String (text string) is that a Cluster Group can have more than one AntiAffinityClassNames values. System.Collections.Specialized.StringCollection has a method called Add which can be used to to add values to the collection. Here is a complete example on how to create such an object, add a couple of values to it and at the end assign it to the AntiAffinityClassNames property of a cluster group:

$value = New-Object System.Collections.Specialized.StringCollection
$value.Add("Domain Controllers")
$value.Add("Infrastructure Server Group")
(Get-ClusterGroup "SCVMM SRV01 Resources").AntiAffinityClassNames = $value

Note that this will overwrite any existing values. As we can see it is not very hard to configure a new value, but it might be harder if you want to preserve existing values remove single items of the existing value and so on. In order to make this easier I have created a PowerShell module which contains 3 script cmdlets for managing AntiAffinityClassNames:

image

As you can see in the cmdlet help there is support for pipeline input, which makes it possible to configure the AntiAffinityClassNames values based on input such as a CSV-file:

image

I have also provided examples for the script cmdlets:

image

 

Installing the AntiAffinityClassNames module

Download and unzip AntiAffinityClassNames.zip in the following location: %userprofile%\Documents\WindowsPowerShell\Modules\AntiAffinityClassNames

Alternatively you may save the module in any of the folders in the $Env:PSMODULEPATH variable or import the module from a custom path (Import-Module <path>\AntiAffinityClassNames). Here is some more examples to get you started:

# Import the module
Import-Module AntiAffinityClassNames

# Example usage of the Get-AntiAffinityClassNames script cmdlet

Get-AntiAffinityClassNames -Cluster cluster01.domain.local

Get-AntiAffinityClassNames -Cluster cluster01.domain.local -ClusterGroup "SC VMM SRV01 Resources"

Get-AntiAffinityClassNames -Cluster cluster01.domain.local | Export-Csv -Path c:\temp\AntiAffinityClassNames_cluster01.csv -NoTypeInformation

# Example usage of the Set-AntiAffinityClassNames script cmdlet

Set-AntiAffinityClassNames -Cluster cluster01.domain.local -ClusterGroup "SC VMM SRV01 Resources" -Value "Domain Controllers"

Set-AntiAffinityClassNames -Cluster cluster01.domain.local -ClusterGroup "SC VMM SRV01 Resources" -Value "Domain Controllers" -Keep

Set-AntiAffinityClassNames -Cluster cluster01.domain.local -ClusterGroup "SC VMM SRV01 Resources" -Value "Domain Controllers" -Verbose

# Example usage of the Remove-AntiAffinityClassNames script cmdlet

Remove-AntiAffinityClassNames -Cluster cluster01.domain.local -ClusterGroup "SC VMM SRV01 Resources" -Clear

Remove-AntiAffinityClassNames -Cluster cluster01.domain.local -ClusterGroup "SC VMM SRV01 Resources" -Value "Domain Controllers"

Remove-AntiAffinityClassNames -Cluster cluster01.domain.local -ClusterGroup "SC VMM SRV01 Resources" -Value "Domain Controllers" -Verbose

 

Resources

MSDN: AntiAffinityClassNames

Failover behavior on clusters of three or more nodes

Understanding Hyper-V Virtual Machine (VM) Failover Policies

Private Cloud: Configuring anti-affinity between VMs on Hyper-V 2008 R2 SP1 and VMM 2012

How to automatically avoid running Exchange VMs on the same Hyper-V server after a host failure

Get started with the Failover Clustering PowerShell-module

Enable Persistent Mode for Cluster Resource Groups using the PowerShell Failover Clustering module

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February 23, 2012 - Posted by | Failover Clustering, Hyper-V R2, Virtualization, Windows PowerShell, Windows Server 2008 R2 | ,

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