All WLDs can be stretched across two availability zones. Availability zones can be in either the same data center but in different racks or server rooms, or they can be in two different data centers in two different geographic locations. They are typically in the same metro area. The VxRail vSAN stretched cluster configuration combines both standard VxRail procedures and automated steps. The steps are performed by using a script from your VCF Development Center that can be copied and run from SDDC Manager. The vSAN Witness is manually deployed and configured, and the SDDC Manager automates the configuration of the VxRail vSAN stretched cluster.

The following general requirements apply to a VCF on VxRail vSAN stretched cluster deployments:

• The Witness is deployed at a third site using the same VMware vSphere version that is used in the VCF on VxRail release.
• All VxRail vSAN stretched cluster configurations must be balanced with the same number of hosts in AZ1 and AZ2.
• A minimum of four nodes are required at each site for the management WLD.
• A minimum of three nodes are required at each site for a VI WLD.

Note: The VI WLD VxRail cluster can only be stretched if the Mgmt WLD VxRail cluster is first stretched.

The following network requirements apply for the Mgmt WLD and the VI WLD VxRail clusters that must be stretched across the AZs in accordance with the VMware VVS design:

• Stretched Layer 2 for the external management traffic
• Routed L3 for vSAN between data node sites
• 5-millisecond RTT between data node sites
• Layer 3 vSAN between each data nodes site and Witness site
• 200-millisecond RTT between data node sites and the Witness site
• DHCP for the Host TEP networks at AZ1 and AZ2
• Stretched Layer 2 for Edge TEP and Uplink networks for Edge Nodes

Note: For the VI WLD, it might be possible to use a different Edge design where the uplink and Edge TEP networks do not need to be stretched. Consult with VMware before deciding on the design if you are not following the VCF guidance.

You cannot stretch a VxRail cluster if remote vSAN datastores are mounted on any VxRail cluster.

Figure 49.    VxRail vSAN stretched cluster network requirements

The following section contains more details about the requirements for the network requirements between sites for each type of WLD.