There are two main types of failover server cluster modes, Active/Passive Mode and Active/Active Clustering Mode.
Active/Passive clustering mode
In Active/Passive clustering mode, one node in the cluster provide cluster services while the other cluster node or nodes remain online but do not provide cluster services to end users. When the active node which is giving the services to the end users fails, the cluster groups previously running on that node are failed over to the passive node, and that node will become the active node and begin serving end users.
Active/Active clustering mode
In Active/Active failover server clustering mode, one instance of the cluster application runs on each node of the cluster. When a failure occurs, two or more instances of the application from the failed node can run on any other cluster node. In Active/Active mode, physical hardware resources on each node are used simultaneously. The disadvantage of Active/Active failover server clustering mode is that if all servers in cluster are running at their maximim capacity and if any node fails, other servers in the node may not be able to handle the end user requests effectively.