MySQL 9.1 Release Notes
As part of a provisioning approach you can use MySQL Enterprise Backup to copy and restore the data from a group member to new members. However you cannot use this technique to directly restore a backup taken from a member running an older version of MySQL to a member running a newer version of MySQL. The solution is to restore the backup to a new server instance which is running the same version of MySQL as the member which the backup was taken from, and then upgrade the instance. This process consists of:
Take a backup from a member of the older group using mysqlbackup. See Section 20.5.6, “Using MySQL Enterprise Backup with Group Replication”.
Deploy a new server instance, which must be running the same version of MySQL as the older member where the backup was taken.
Restore the backup from the older member to the new instance using mysqlbackup.
Upgrade MySQL on the new instance, see Chapter 3, Upgrading MySQL.
Repeat this process to create a suitable number of new instances, for example to be able to handle a failover. Then join the instances to a group based on the Section 20.8.3.3, “Group Replication Online Upgrade Methods”.`