Disk Witness in Quorum - switch to a different Quorum Disk

Question

We've got 2 storage arrays attached to a Hyper-V cluster. We're going to decommission the older array, but one of its disks is a Disk Witness in Quorum.

In Failover Cluster Manager, how do we switch the Disk Witness in Quorum to an available storage disk on the newer array, ?

Afterwards, we can Offline the Quorum Disk, but there's no Delete option in Failover Cluster Manager ?

Thanks

Answer 1

Hi Albert Pang,

To switch your Disk Witness to the newer array, you must run the Configure Cluster Quorum Settings wizard since you cannot modify the disk designation directly. Right-click your cluster name in Failover Cluster Manager, navigate to More Actions, and launch this wizard to select the new storage LUN from your Available Storage pool. Completing this configuration will seamlessly promote the new disk to handle the Disk Witness role while automatically demoting your old disk into the Available Storage group without interrupting the core cluster service, known as clussvc.

Regarding the missing delete option, Failover Cluster Manager uses removal terminology for storage objects rather than deletion. Once the quorum wizard shifts the old disk into Available Storage, you should right-click the old disk under the Disks node and take it offline directly within the cluster interface to ensure no other nodes attempt to claim it. After taking it offline, right-click it again and select Remove to drop the logical cluster hold.

Finally, you must log into the specific Hyper-V node that last owned the disk to clean up the operating system handles. Launch the Windows Disk Management console by running diskmgmt.msc and ensure the old disk is marked offline at the host level. Once this operating system verification is complete, you can safely unmap the LUN from your old storage array using your storage vendor's management interface.

Hope this answer brought you some useful information. If it did, please hit “accept answer”. Should you have any questions, feel free to leave a comment.

VP

Answer 2

Hi Albert Pang,

How is your issue going? Has it been resolved yet? If it has, please consider accepting the answer as it helps others sharing the same problem benefit too. Thank you :)

VP

Answer 3

Use Failover Clustering tools to move the witness, then safely remove the old disk.

1. Add or identify the new disk for quorum
   • Present a new LUN from the newer array to all cluster nodes.
   • Add it to the cluster so it appears as Cluster Available Storage and is visible as a clustered disk.
2. Switch the quorum disk to the new LUN
   • Use PowerShell on a cluster node:

          # See current quorum configuration
          Get-ClusterQuorum
          
          # List clustered disks so the new disk name can be identified
          Get-ClusterResource | Where-Object {$_.ResourceType -eq 'Physical Disk'}
          
          # Set the new disk as the disk witness (replace with the new disk resource name)
          Set-ClusterQuorum -DiskWitness "Cluster Disk X"
     

   • Set-ClusterQuorum -DiskWitness configures the cluster to use the specified clustered disk as the disk witness. Only one witness (disk/file/cloud) can be configured at a time, so this command replaces the old disk witness with the new one.
3. Verify quorum
   • Run Get-ClusterQuorum again to confirm the quorum mode is Node majority with witness (disk) and that the new disk is listed as the Disk Witness.
   • Optionally run the Validate Quorum Configuration test (via Validate a Configuration Wizard or Test-Cluster) to confirm the configuration is healthy.
4. Decommission the old quorum disk
   • In Failover Cluster Manager or via PowerShell, move any roles off the old disk if it is still part of any groups.
   • Remove the old disk from the cluster:

          # Identify the old disk resource
          Get-ClusterResource "Cluster Disk Y" | Remove-ClusterResource
     

   • Once it is no longer a clustered resource and not used by any roles, unpresent the LUN from all nodes and decommission it on the storage array.

This approach cleanly switches the disk witness to the new storage and avoids any quorum loss while retiring the old array.

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References:

• Set-ClusterQuorum
• What is a quorum witness?
• Understanding cluster and pool quorum
• Configuring Witness resource troubleshooting guide