vSAN stretched-cluster is a VMware solution that supports synchronous I/O on a vSAN datastore over distance and is supported on VxRail. A vSAN stretched-cluster enables site-level failure protection with no loss of service or loss of data.

If you plan to deploy a vSAN stretched-cluster on VxRail, note the following requirements:

• Three data center sites: two data center sites (Primary and Secondary) host the VxRail infrastructure, and the third site supports a witness to monitor the stretched-cluster.
• A minimum of three VxRail nodes in the Primary site, and a minimum of three VxRail nodes in the Secondary site
• A minimum of one top-of-rack switch for the VxRail nodes in the Primary and Secondary sites
• An ESXi instance at the Witness site

The vSAN stretched-cluster feature has strict networking guidelines, specifically for the WAN, that must be adhered to for the solution to work.

Figure 14.          vSAN Stretched Cluster Topology

More detailed information about vSAN stretched-cluster and the networking requirements can be found in the Dell-EMC VxRail vSAN Stretched Cluster Planning Guide.