Deploying Group Replication in Single-Primary Mode increases. The maximum number of instances which can be used in a group is nine. For more information see Section 18.1.4.2, “Failure Detection” . This section explains the configuration settings required for MySQL Server instances that you want to use for Group Replication. For background information, see Section 18.3, “Requirements and Limitations” . For Group Replication, data must be stored in the InnoDB transactional storage engine (for details of why, see Section 18.3.1, “Group Replication Requirements” ). The use of other storage engines, including the temporary  MEMORY  storage engine, might cause errors in Group Replication. Set the disabled_storage_engines  system variable as follows to prevent their use: disabled_storage_engines="MyISAM,BLACKHOLE,FEDERATED,ARCHIVE,MEMORY" Note that with the  MyISAM  storage engine disabled, when you are upgrading a MySQL instance to a release where  mysql_upgrade  is still used (before MySQL 8.0.16),  mysql_upgrade  might fail with an error. To handle this, you can re-enable that storage engine while you run  mysql_upgrade , then disable it again when you restart the server. For more information, see Section 4.4.5, “mysql_upgrade — Check and Upgrade MySQL Tables” . The following settings configure replication according to the MySQL Group Replication requirements. These settings configure the server to use the unique identifier number 1, to enable Section 17.1.3, “Replication with Global Transaction Identifiers” , and to allow execution of only statements that can be safely logged using a GTID. Up to and including MySQL 8.0.20, the following setting is also required: This setting disables checksums for events written to the binary log, which default to being enabled. From MySQL 8.0.21, Group Replication supports the presence of checksums in the binary log and can use them to verify the integrity of events on some channels, so you can use the default setting. For more details, see Section 18.3.2, “Group Replication Limitations” . If you are using a version of MySQL earlier than 8.0.3, where the defaults were improved for replication, you also need to add these lines to the member’s option file. If you have any of these system variables in the option file in later versions, ensure that they are set as shown. For more details see Section 18.3.1, “Group Replication Requirements” . binlog_checksum=NONE server_id=1 gtid_mode=ON enforce_gtid_consistency=ON log_bin=binlog log_slave_updates=ON binlog_format=ROW master_info_repository=TABLE relay_log_info_repository=TABLE transaction_write_set_extraction=XXHASH64 Replication Framework Storage Engines 18.2.1.2 Configuring an Instance for Group Replication •Storage Engines •Replication Framework •Group Replication Settings 3703