The cluster resource could not be deleted since it is a core resource

The last month, I wanted to change the Witness of a cluster from a Cloud Witness to a File Share Witness. The cluster is a 2-node S2D cluster and as discussed with Microsoft, Cloud Witness should not be used with a 2-node cluster. If the Cloud Witness fails (for example when subscription has expired), the cluster can crashes. I’ve experienced this in production. So, all my customers, I decided to change the cloud witness to file share witness.

Naivly, I tried to change the Cloud Witness to a File Share witness. But it doesn’t work 🙂 You’ll get this message: The cluster resource could not be deleted since it is a core resource. In this topic I’ll show you the issue and the resolution

Issue

As you can see below, my cluster is using a Cloud Witness to add an additional vote.

So, I decide to replace the Cloud Witness by a File Share Witness. I right click on the cluster | more Actions | Configure Cluster Quorum Settings.

Then I choose Select the quorum witness.

I select configure a file share witness.

I specify the file share path as usual.

To finish I click next and it should replace the cloud witness by the file share witness.

Actually no, you should get the following error message.

If you check the witness state, it is offline.

This issue occurs because we can’t remove cluster core resources. So how I remove the Cloud Witness?

Resolution

To remove the Cloud Witness, choose again to configure the cluster quorum and this time select Advanced Quorum Configuration.

Then select Do not configure a quorum witness.

Voilà, the Cloud Witness is gone. No you can add the File Share Witness.

In the below screenshot you can see the configuration to add a file share witness to the cluster.

Now the file share witness is added to the cluster.

Conclusion

If you want to remove a Cloud Witness or a File Share Witness, you have first to not configure a witness for the quorum. Then you can add the witness type you want.