Very similar to the local data center design described in the previous section is the Remote and Branch Offices design because it is a single-site deployment. Two-node clusters have traditionally not been possible with vSAN because there is a three host minimum to make sure that components can properly be protected. However, the former design requirements of minimum of a three-node configuration is not cost-effective for very small ROBO deployments. For this reason, VMware introduced a two-node design.

However, a two-node design can lead to split brain configurations when a failure occurs. Hence, a witness node at a third site is required to avoid that failure condition. The witness node is a VM that can be installed at the nearest data center site. It requires a round-trip latency of 200 ms.

vSAN 6.2 can be configured from the configuration wizard, allowing for you to setup a two-node cluster with a witness, allowing for smaller configurations of vSAN. This is popular with smaller environments.

 

For more information relating to service provider use cases for ROBO deployments, see the vCAT-SP paper, VMware vSAN Two-Node Architecture Service Provider Use Cases (https://www.vmware.com/files/pdf/vcat/vmw-virtual-san-two-node-architecture-service-provider-use-cases.pdf).