You can create a SyncIQ domain to increase the speed at which failback is performed for a replication policy. Because you can fail back only synchronization policies, it is not necessary to create SyncIQ domains for copy policies.
Failing back a replication policy requires that a SyncIQ domain be created for the source directory. OneFS automatically creates a SyncIQ domain during the failback process. However, if you intend on failing back a replication policy, it is recommended that you create a SyncIQ domain for the source directory of the replication policy while the directory is empty. Creating a domain for a directory that contains less data takes less time.