An N-to-N configuration refers to multiple service groups that run on multiple servers, with each service group capable of being failed over to different servers. For example, consider a four-node cluster in which each node supports three critical database instances.
Figure: N-to-N configuration shows an N to N cluster failover configuration.
If any node fails, each instance is started on a different node. this action ensures that no single node becomes overloaded. This configuration is a logical evolution of N + 1; it provides cluster standby capacity instead of a standby server.
N-to-N configurations require careful testing to ensure that all applications are compatible. You must specify a list of systems on which a service group is allowed to run in the event of a failure.