On the donor, the clone user requires the BACKUP_ADMIN privilege for accessing and transferring data from the donor, and for blocking DDL during the cloning operation.

On the recipient, the clone user requires the CLONE_ADMIN privilege for replacing recipient data, blocking DDL during the cloning operation, and automatically restarting the server. The CLONE_ADMIN privilege includes BACKUP_ADMIN and SHUTDOWN privileges implicitly.

The donor and recipient must have the same MySQL server version. The clone plugin is supported in MYSQL 8.0.17 and higher.

mysql> SHOW VARIABLES LIKE 'version';
 +---------------+--------+
| Variable_name | Value  |
+---------------+--------+
| version       | 8.0.17 |
+---------------+--------+

The donor and recipient MySQL server instances must run on the same operating system and platform. For example, if the donor instance runs on a Linux 64-bit platform, the recipient instance must also run on that platform. Refer to your operating system documentation for information about how to determine your operating system platform.

The recipient must have enough disk space for the cloned data. By default, recipient data is removed prior to cloning the donor data, so you only require enough space for the donor data. If you clone to a named directory using the DATA DIRECTORY clause, you must have enough disk space for the existing recipient data and the cloned data. You can estimate the size of your data by checking the data directory size on your file system and the size of any tablespaces that reside outside of the data directory. When estimating data size on the donor, remember that only InnoDB data is cloned. If you store data in other storage engines, adjust your data size estimate accordingly.

InnoDB permits creating some tablespace types outside of the data directory. If the donor MySQL server instance has tablespaces that reside outside of the data directory, the cloning operation must be able access those tablespaces. You can query the INFORMATION_SCHEMA.FILES table to identify tablespaces that reside outside of the data directory. Files that reside outside of the data directory have a fully qualified path to a directory other than the data directory.

mysql> SELECT FILE_NAME FROM INFORMATION_SCHEMA.FILES;

Plugins that are active on the donor, including any keyring plugin, must also be active on the recipient. You can identify active plugins by issuing a SHOW PLUGINS statement or by querying the INFORMATION_SCHEMA.PLUGINS table.

The donor and recipient must have the same MySQL server character set and collation. For information about MySQL server character set and collation configuration, see Section 10.15, “Character Set Configuration”.

The same innodb_page_size and innodb_data_file_path settings are required on the donor and recipient. The innodb_data_file_path setting on the donor and recipient must specify the same number of data files of an equivalent size. You can check variable settings using SHOW VARIABLES syntax.

mysql> SHOW VARIABLES LIKE 'innodb_page_size';
mysql> SHOW VARIABLES LIKE 'innodb_data_file_path';

If cloning encrypted or page-compressed data, the donor and recipient must have the same file system block size. For page-compressed data, the recipient file system must support sparse files and hole punching for hole punching to occur on the recipient. For information about these features and how to identify tables and tablespaces that use them, see Section 5.6.7.4, “Cloning Encrypted Data”, and Section 5.6.7.5, “Cloning Compressed Data”. To determine your file system block size, refer to your operating system documentation.

A secure connection is required if you are cloning encrypted data. See Configuring an Encrypted Connection for Cloning.

The clone_valid_donor_list setting on the recipient must include the host address of the donor MySQL server instance. You can only clone data from a host on the valid donor list. A MySQL user with the SYSTEM_VARIABLES_ADMIN privilege is required to configure this variable. Instructions for setting the clone_valid_donor_list variable are provided in the remote cloning example that follows this section. You can check the clone_valid_donor_list setting using SHOW VARIABLES syntax.

mysql> SHOW VARIABLES LIKE 'clone_valid_donor_list';

There must be no other cloning operation running. Only a single cloning operation is permitted at a time. To determine if a clone operation is running, query the clone_status table. See Monitoring Cloning Operations using Performance Schema Clone Tables.

The clone plugin transfers data in 1MB packets plus metadata. The minimum required max_allowed_packet value is therefore 2MB on the donor and the recipient MySQL server instances. A max_allowed_packet value less than 2MB results in an error. Use the following query to check your max_allowed_packet setting:

mysql> SHOW VARIABLES LIKE 'max_allowed_packet';

Undo tablespace file names on the donor must be unique. When data is cloned to the recipient, undo tablespaces, regardless of their location on the donor, are cloned to the innodb_undo_directory location on the recipient or to the directory specified by the DATA DIRECTORY [=] 'clone_dir' clause, if used. Duplicate undo tablespace file names on the donor are not permitted for this reason. As of MySQL 8.0.18, an error is reported if duplicate undo tablespace file names are encountered during a cloning operation. Prior to MySQL 8.0.18, cloning undo tablespaces with the same file name could result in undo tablespace files being overwritten on the recipient.

To view undo tablespace file names on the donor to ensure that they are unique, query INFORMATION_SCHEMA.FILES:

mysql> SELECT TABLESPACE_NAME, FILE_NAME FROM INFORMATION_SCHEMA.FILES
       WHERE FILE_TYPE LIKE 'UNDO LOG';

For information about dropping and adding undo tablespace files, see Section 15.6.3.4, “Undo Tablespaces”.

By default, the recipient MySQL server instance is restarted (stopped and started) automatically after the data is cloned. For an automatic restart to occur, a monitoring process must be available on the recipient to detect server shutdowns. Otherwise, the cloning operation halts with the following error after the data is cloned, and the recipient MySQL server instance is shut down:

ERROR 3707 (HY000): Restart server failed (mysqld is not managed by supervisor process).

This error does not indicate a cloning failure. It means that the recipient MySQL server instance must be started again manually after the data is cloned. After starting the server manually, you can connect to the recipient MySQL server instance and check the Performance Schema clone tables to verify that the cloning operation completed successfully (see Monitoring Cloning Operations using Performance Schema Clone Tables.) The RESTART statement has the same monitoring process requirement. For more information, see Section 13.7.8.8, “RESTART Statement”. This requirement is not applicable if cloning to a named directory using the DATA DIRECTORY clause, as an automatic restart is not performed in this case.

Several variables control various aspects of a remote cloning operation. Before performing a remote cloning operation, review the variables and adjust settings as necessary to suit your computing environment. Clone variables are set on recipient MySQL server instance where the cloning operation is executed. See Section 5.6.7.12, “Clone System Variables”.