Configure Virtual SAN Stretched Cluster

Configure a Virtual SAN cluster that stretches across two geographic locations or sites.

Prerequisites

Verify that you have a minimum of three hosts: one for the preferred site, one for the secondary site, and one host to act as a witness.
Verify that you have configured one host to serve as the witness host for the stretched cluster. Verify that the witness host is not part of the Virtual SAN cluster, and that it has only one VMkernel adapter configured for Virtual SAN data traffic.
Verify that the witness host is empty and does not contain any components. To configure an existing Virtual SAN host as a witness host, first evacuate all data from the host and delete the disk group.

Navigate to the Virtual SAN cluster in the vSphere Web Client.
Click the Configure tab.
Under Virtual SAN, click Fault Domains and Stretched Cluster.
Click the Stretched Cluster Configure button to open the stretched cluster configuration wizard.
Select the fault domain that you want to assign to the secondary site and click >>.
The hosts that are listed under the Preferred fault domain are in the preferred site.
Click Next.

Select a witness host that is not a member of the Virtual SAN stretched cluster and click Next.

Select the mode for storage devices on the witness host to be claimed, and click Next.

Option	Description
Automatic	Claims all empty devices on the included hosts for Virtual SAN. Virtual SAN in automatic mode claims only local devices on the ESXi hosts in the cluster. You can add any remote non-shared devices manually.
Manual	Requires manual claiming of the devices on the included hosts. New devices on the host are not added to Virtual SAN. With the manual mode, two methods of organizing devices into disk groups exist, semi-automatic and manual. Note: When you use this mode, a Virtual SAN datastore is created, with the initial size of zero bytes. The datastore remains unusable until you manually claim devices.