VxRail supports a 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 utilize node removal to convert into a 2-node cluster configuration. However a 2-node cluster configuration can be expanded through the addition of new nodes, up to the 64-node cluster limit. Users can still benefit from VxRail automated lifecycle management.
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 installed on an ESXi host which must reside outside of the 2-node cluster, i.e. 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.