All vRealize Operations clusters consist of a master node (primary node), an optional replica node for high availability or continously availability, optional data nodes, and optional remote collector nodes.

When you install vRealize Operations, you use a vRealize Operations vApp deployment to create role-less nodes. After the nodes are created and have their names and IP addresses, you use an administration interface to configure them according to their role.

You can create role-less nodes all at once or as needed. A common as-needed practice might be to add nodes to scale out vRealize Operations to monitor an environment as the environment extends larger.

The following node types make up the vRealize Operations analytics cluster:

Master Node
The master node is the primary node and the initial, required node in vRealize Operations. All other nodes are managed by the primary node.

In a single-node installation, the primary node manages itself, has adapters installed on it, and performs all data collection and analysis.

Data Node
In larger deployments, additional data nodes have adapters installed and perform collection and analysis.

Larger deployments usually include adapters only on the data nodes so that primary and replica node resources can be dedicated to cluster management.

Replica Node
To use vRealize Operations high availability (HA) and continous availability (CA) the cluster requires that you convert a data node into a replica of the primary node.

The following node types are a member of the vRealize Operations cluster but not part of the analytics cluster:

Remote Collector Node
Distributed deployments might require a remote collector node that can navigate firewalls, interface with a remote data source, reduce the bandwidth across data centers, or reduce the load on the vRealize Operations analytics cluster. Remote collectors only gather objects for the inventory, without storing data or performing analysis. In addition, remote collector nodes might be installed on a different operating system than the rest of the cluster.
Witness Node
To use vRealize Operations continuous availability (CA), the cluster requires that you have a witness node. Each vRealize Operations cluster can have only one witness node. If the network connection between the two fault domains is lost, the witness node acts as a decision maker regarding the availability of vRealize Operations.