Configure vSAN Stretched Cluster fails with error - "Witness host already in vSAN stretched cluster."

Products

• VMware vSAN

Issue/Introduction

Symptoms:

• vSAN stretched cluster was previously configured, but currently on vCenter the Witness & vSAN Stretched cluster configuration are not visible:

  

• When trying to Configure Stretched Cluster, the Wizard fails with error: "Witness host already in vSAN stretched cluster."

• vSAN object are in the Reduced Availability state.

Environment

VMware vSAN 7.x

VMware vSAN 8.x

Cause

Possible causes:

1. This issue can occur when the witness host is added to the cluster via CLI.

2. Or, when a Stretched Cluster is moved from vCenter to another without removing the witness.

 

In both of the above cases, the vCenter would not be aware of the configuration of witness in the vSAN cluster, thus it does not populate this information in the vSphere Client.

It will also be unable to push this configuration when configuring stretched cluster as the witness is already part of the vSAN cluster, thus the error is seen.

Resolution

To resolve this issue follow the below steps:

1. Validate that the vSAN Witness is not part of any other cluster, by running this command in it's SSH: esxcli vsan cluster get

   

   In the output, the Sub-Cluster UUID should match the Sub-Cluster UUID output for the same command run on the data node. 

2. Validate if the disk group is present on the vSAN Witness host, using command: vdq -iH

3. Validate that the objects on the vSAN cluster are in the Reduced availability state, by running this command on the data nodes: esxcli vsan debug object health summary get

4. Once verified, run this command to delete the disk group from the vSAN witness: esxcli vsan storage remove -s <mpx.###>

   Where <mpx.###> - is the name of the cache (SSD) device from the step 2 command's output.

5. Run this command on vSAN witness to make the vSAN witness leave the cluster it is currently a part of: esxcli vsan cluster leave

6. Now, configure the vSAN stretched cluster from the vSphere Client and it will be successful. Manually Configure vSAN Stretched Cluster.

Additional Information

Other possible issue/cause with similar error: Configuring Stretched Cluster Results in "A specified parameter was not correct - Witness host already configured in stretched cluster"