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 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 Primary Node.