2.2.1 Number of Nodes
vSAN supports clusters with a variable number of nodes depending on the implemented version of the product. The number of nodes in a cluster defines the behavior of the cluster in case of failure of a node.
• Two-node clusters (vSAN 6.1 and later) hold up to two replicas of the data and require an additional witness residing on a third host outside the cluster.
• Three-node clusters hold up to two replicas of the data and a witness, all residing on different hosts of the cluster.
• Four-node or more clusters (up to 64 hosts for vSAN 6.x, or up to 32 hosts for earlier releases) hold three or more copies of the data, all residing on different hosts of the cluster.