vSAN stretched clusters are deployed across two sites in an Active/Active configuration. An identical number of ESXi hosts was required in versions earlier than vSAN 6.6/VxRail 4.5.070 to ensure a balanced distribution of resources. Starting with vSAN 6.6/VxRail 4.5.070, unbalanced configurations are supported; however, we recommend having an identical number of ESXi hosts across the two sites. VM and Host Affinity rules must be set for an unbalanced configuration.
Each data site is configured as a Fault Domain. An externally available third site houses a Witness appliance, which makes up the third Fault Domain.
You must plan the VxRail stretched cluster deployment before installation. Depending on the number of nodes in the VxRail cluster, you can: