Possible Owner in Failover Cluster. Part 3

Possible Owner

• Part 1 covers some theory and GUI configuration.
• Part 2 will focus on setting Preferred Owners with Powershell.
• Part 3 will explain logic behind Possible Owners in PowerShell function.
• Part 4 will cover the last step - setting anti-affinity groups.
• Part 5 will describe reporting of current configuration in the cluster.

Today let’s focus on logic behind Possible Owners feature in Failover clustering.

General concept

This is a little trickier. Before a VM can have its 'Possible Owner' property set, it must be on one of the Hyper-V nodes first. There can be a few scenarios - VM1 and 4 Hyper-V Nodes: Node1-4.

• I want to reset configuration to defaults - in other words set it to Node1-4
• I want to set configuration to Node2 and VM is on Node2
• I want to set configuration to Node1-2 and VM is on Node2
• I want to set configuration to Node1-2 and VM is on Node3 or Node4   First, in the begin{} block I will:
• create PSSesion to the Cluster
• if $PossibleOwner not set, I’ll assign all current cluster nodes to it
• If $PossibleOwner is set I will validate whether provided nodes exists   Then I’ll loop through each VM. If it’s found then:
• I’ll get it’s current configuration

• Compare to expected and if there’s a mismatch I’ll proceed

  1. Scenario 1 is the simplest - I’ll just set PossibleOwner to all nodes.
  2. Scenario 2 and 3 are similar, but provided parameter $PossibleOwner will be used
  3. Scenario 4 requires some additional work:
     • First, I need to reset PossibleOwner to default to allow migration
       • If the VM is turned on - I’ll use Live Migration
       • If the VM is turned off - I’ll use Quick Migration
     • After migration was successful I can finally set PossibleOwner to desired state
• In the end I’ll return a custom object for each processed VM with 4 parameters:
  • Cluster
  • VMName
  • CurrentNode VM is
  • OwnerNode value which is the PossibleOwner we wanted to achieve
• And finally will remove PSSession

Full Script

Here’s the full script:

And here’s the output from PowerShell Core:

• Reset to defaults

• Set to two nodes. VMs are on one of the nodes

• Set to two different nodes than VMs are on

Summary

This one requires a little bit of more work than before. Mainly because involves moving VMs between nodes. One last to go and we’ll get into reporting :)