VMware vSAN stretched cluster supports synchronous I/O on a local vSAN data store on two sites that are separated geographically.
The VMware vSAN stretched cluster enables site-level failure protection with no loss of service or loss of data.
If you plan to deploy a VMware vSAN stretched cluster on VxRail, note the following requirements:
- The VxRail nodes must be populated with the compatible disk drives so that a VMware vSAN data store can be configured.
- The compute and storage resources that are planned for the cluster should be doubled. It is best practice to reserve 50 percent of resource capacity in the cluster for failure protection.
- This cluster type requires a witness. A witness is a small virtual appliance that monitors the health of the stretched cluster.
- Network connectivity is required between the stretched cluster and the witness.
- A VMware ESXi instance is required at the Witness site.
- Three data center sites are required for this solution: a primary and secondary data center site to host the VxRail infrastructure, and a third site to supports a witness to monitor the stretched cluster.
- A minimum of one ToR switch for the VxRail nodes in the primary site and in the secondary site.
The VMware vSAN stretched cluster feature has strict networking guidelines for the WAN to support the solution.
See Dell VxRail vSAN Stretched Cluster Planning Guide for detailed information about vSAN stretched cluster and the networking requirements.