Moving vSAN Hosts/Nodes from one cluster to another within the same vCenter.

Products

• VMware vSAN

Issue/Introduction

This is an abbreviated version of the article: Moving a vSAN cluster from one vCenter Server to another

Environment

vCenter 8.x

vCenter 7.x

vSphere/ESXi 8.x

vSphere/ESXi 7.x

Cause

Often it is necessary to move vSAN hosts into a new cluster object due to issues with the original cluster that do not otherwise have any bearing on the running state of vSAN.

Resolution

The following should be run with all due caution. It is important to ensure that good backups are available as any such change carries a degree of risk. This process seeks to mitigate that risk.

 

1. In vCenter, create a new Cluster object. (Right-click on the Datacenter where the current cluster resides and select New Cluster)
2. Enable vSAN along with required services matching the original cluster parameters such as Encryption and or Deduplication and Compression, and any image management settings. Do enable Do not enable HA or DRS in this cluster until after the process in this article.
3. Choose the option to Skip Quickstart in the new cluster.
4. IMPORTANT!!!!!!  The following MUST BE RUN on ALL ESXi hosts in the cluster via CLI prior to the next steps!!! This will ensure when the hosts are disconnected and reconnected, they will not lose their unicast configurations and therefore their connectivity between hosts. If this step is skipped, the unicast address table will be cleared and data availability will be affected temporarily until the table is manually repopulated. 
   1. esxcfg-advcfg -s 1 /VSAN/IgnoreClusterMemberListUpdates
   2. Backup the current unicast list by typing "esxcli vsan cluster unicastagent list" and copying output to a notepad
5. Disconnect one host from vCenter by right clicking the host then Connection -> Disconnect.
6. Run "esxcli vsan cluster get" and verify the correct number of hosts. 
7. Click and Drag one host from the old cluster to the new cluster.
8. Once in the new cluster right click the host and select Connection -> Connect
9. Before moving on to the next host, verify there is host-to-host vSAN communication. Run the command "esxcli vsan cluster get" and take note of the host count to ensure the count matches.
   1. It is good to practice the above command each time a host is disconnected, moved, and connected. If the host is not communicating, i.e. the host count is less than expected, then it is highly likely a critical step has been missed.
10. Please review the steps and ensure each host's unicast tables are complete and host-to-host communication on the vSAN network is fully functional. To verify unicast agent table, use below command:
    1. esxcli vsan cluster unicastagent list
11. Once the first host is moved and connectivity checks are performed, repeat this process with the remaining hosts. Please be certain to follow the steps carefully and check the cluster membership along the way to prevent any data availably impacts.
12. Once all hosts have been added to the new cluster and access to the VMs has been verified, verify there are no new alerts in the vSAN Skyline health check (
13. revert the hosts' unicast table configuration. This procedure should be completed at the completion of the migration, and before the hosts are rebooted next. Check the cluster membership remains the same between setting each host back to default.
    1. esxcfg-advcfg -s 0 /VSAN/IgnoreClusterMemberListUpdates
    2. esxcli vsan cluster get
14. Rerun the vSAN skyline health test to ensure the vCenter is authoritative alert has cleared.

Additional Information

For issues that may arise with Unicast tables please see: Configuring vSAN Unicast networking from the command line

For full details, please see: Moving a vSAN cluster from one vCenter Server to another