What unidirectional port mirroring is

The unidirectional port mirroring feature enables you to increase the performance throughput by using the ISLs effectively for sending and receiving the data for NVRAM mirroring. By enabling this feature, one link in an FC-VI interconnect is used for outgoing and the other for incoming data traffic in a MetroCluster configuration.

The FC-VI interconnect link to be used for outgoing and incoming data traffic is identified based on System Serial Number of the nodes in a MetroCluster configuration. The node with higher System Serial Number uses FC-VI link 0 for outgoing data traffic and FC-VI link 1 for incoming data traffic. The partner node will, therefore, use FC-VI link 0 for incoming data traffic and FC-VI link 1 for outgoing data traffic.
Note: If any of the FC-VI link between the MetroCluster nodes fails, the FC-VI link fails over to the other available FC-VI link. When the failed FC-VI link is restored, the MetroCluster configuration resumes using earlier link. The failover temporarily causes logs to be unsynchronized.