Add an existing populated datastore to a Datastore cluster

I had a question recently on creating a Datastore cluster. The question was "I have datastores with VM's already on them, can I create a datastore cluster with these volumes?". The answer is Yes! I could not find documentation on this. Most of the documentation out there shows you how to create Datastore Clusters from scratch, but really they don't address currently populated volumes. Of course you do want to follow the guidelines for creating a datastore cluster (make sure they are not replicated volumes, same storage characteristics, VMFS or NFS volumes and correct tier of storage) .  You would go through the same wizard to create the datastore cluster. Simply select populated or unpopulated datastores that you want to include in the cluster. From the VM's prospective, the storage volume will update to the new cluster name.

Issue while creating a storage cluster – next greyed out

Recently I ran into an issue creating some new storage clusters on two different vCenter servers. I had a problem where I was selecting the host cluster to create a storage cluster within, but the next button was greyed out.

I went through my own troubleshooting steps. 1. Did there have to be more than one datastore in order to create a cluster? No, because you can create a cluster with even local storage (on the same host) with one disk. 2. Are both the datastores the same? Yes, both on fiber (you cannot create a cluster with mixed datastore types (NFS / VMFS). 3. Are datastores stored between different sites? – No, both are in the same datacenter. 4. Do I have any replicated datastores? – No, not for this cluster. 5. Are all the hosts in the cluster esxi 5? Yes, all hosts are supported.

I also started to wonder… Do they need to be unformatted in order to do the initial setup for a storage cluster? No. Do they need to be at a certain VMFS level to join the cluster? Yes, Version 5.x or above. Are the datastores currently part of any other storage cluster? No.

After beating my head against it for a while it turns out you have to select the top level datacenter and then unselect all of the unwanted clusters to join the storage group. I had this happen on two different vCenters with build 455964. I then went to another environment with the same build and did not have this issue.

For more info on the general practice of creating a datastore cluster, visit