VxRail supports a fixed 2-node vSAN cluster configuration. With its small footprint, it can be an appropriate, cost-effective solution for locations with limited space and workload requirements. The support requires that the configuration to be a brand-new deployment which means existing clusters cannot use node removal to convert into a 2-node cluster configuration. Cluster expansion is not supported therefore this solution should be targeted for specific use cases. Users can still benefit from VxRail automated lifecycle management.

Figure 27.          Network configuration for a 2-node vSAN cluster that is deployed with direct-connect option

The 2-node vSAN cluster on VxRail can be deployed in a switch configuration or a direct-connect configuration. In a switch configuration, all ports are connected to the switch. In a direct-connect configuration, the ports for vSAN and vMotion traffic are directly connected. A witness provides quorum for the cluster. The Witness is a virtual appliance that is installed on an ESXi host which must reside outside of the 2-node cluster, that is in another data center or a physical host in the same rack/location. The Witness has individual connections to both nodes which requires VLANs to separate Witness management traffic from vSAN traffic. The configuration only supports mirroring (FTT=1). Witness host is used as the tiebreaker. Each node and the Witness are an individual fault domain for a total three in the cluster.

A special workflow in the First Run experience is used to deploy the 2-node cluster. The workflow includes the setup of the Witness appliance and Witness traffic separation. The configuration must use a customer-supplied vCenter for management. With only two data nodes in the cluster, users need be cognizant of the cluster load to prevent data unavailability in case of a node failure and a single node servicing the entire cluster workload.

For more information, refer to the 2-node vSAN Cluster on VxRail planning guide: https://www.dellemc.com/resources/en-us/asset/technical-guides-support-information/products/converged-infrastructure/h17566-vsan-2node-cluster-on-vxrail-planning-guide.pdf