If you have to upgrade a MetroCluster configuration, you should be aware of some important requirements.
Patch upgrades to MetroCluster configurations can be performed with automatic non-disruptive upgrade (NDU) procedure.
Starting with ONTAP 9.3, major upgrades to MetroCluster configurations can be performed with automatic non-disruptive upgrade (NDU) procedure. On systems running ONTAP 9.2 or earlier, major upgrades to MetroCluster configurations must be performed with the NDU procedure that is specific to MetroCluster configurations.
You can verify the ONTAP version by using the version command.
For nondisruptive upgrade in two-node clusters, the clusters must be upgraded one node at a time.
During MetroCluster healing, the mirrored aggregates are resynchronized. You can verify if the MetroCluster configuration is in this state by using the storage aggregate plex show -in-progress true command. If any aggregates are being synchronized, you should not perform an upgrade until the resynchronization is complete.
To avoid issues with upgrade or revert operations, do not attempt an unplanned switchover during an upgrade or revert operation unless all nodes on both clusters are running the same version of ONTAP.
Data LIFs for the destination SVMs are not required to be up or to be on their home nodes.
Root aggregates at the DR site are offline during certain phases of switchover.