You can use the new installation to create a primary node during the first installation of vRealize Operations. With the primary node in place, you can then start adding more nodes to form a cluster and then define an environment for your organization.
In a single-node clusters, administration and data is on the same primary node. A multiple-node cluster includes one primary node and one or more data nodes. In addition, there might be remote collector nodes, and there might be one replica node used for high availability. For continuous availability, you need a witness node and an even number of data nodes including the primary node. For more information on creating a primary node, see About the vRealize Operations Master Node.