When you add new instances to an InnoDB ReplicaSet you need to provision the instances with the existing data that the ReplicaSet contains. You can do this provisioning automatically using one of the following methods:
MySQL Clone: Takes a snapshot from an online instance and then replaces any data on the new instance with the snapshot. MySQL Clone is well suited for joining a new blank instance to an InnoDB ReplicaSet. MySQL Clone does not rely on there being a complete binary log of all transactions applied by the InnoDB ReplicaSet.Warning
When you add an instance, the MySQL Clone operation destroys all the instance's previous data.
Incremental Recovery: Relies on MySQL Replication to apply all missing transactions on the new instance. Incremental Recovery is the fastest method if only a few transactions are missing on the new instance. However, you can only use this method if at least one online instance of the InnoDB ReplicaSet has a complete binary log, which contains the entire transaction history of the InnoDB ReplicaSet.
You cannot use this method:
If you have purged the binary logs from all members.
If you enabled the binary log after databases already existed in the instance.
If you have many transactions to apply, there could be a substantial delay before the instance can join the InnoDB ReplicaSet.
When an instance is joining a ReplicaSet, recovery is used in much the same way that it is in InnoDB Cluster. MySQL Shell attempts to automatically select a suitable recovery method. If it is not possible to choose a method safely, MySQL Shell prompts for what to use. For more information, see Section 7.4.6, “Using MySQL Clone with InnoDB Cluster”. This section covers the differences when adding instances to a ReplicaSet.