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5.23.1.1 Restoring an NDB backup to a previous version of NDB Cluster

You may encounter issues when restoring a backup taken from a later version of NDB Cluster to a previous one, due to the use of features which do not exist in the earlier version. Some of these issues are listed here:

  • utf8mb4_ai_ci character set.  Tables created in NDB 8.0 by default use the utf8mb4_ai_ci character set, which is not available in NDB 7.6 and earlier, and so cannot be read by an ndb_restore binary from one of these earlier versions. In such cases, it is necessary to alter any tables using utf8mb4_ai_ci so that they use a character set supported in the older version prior to performing the backup.

  • Table metadata format.  Due to changes in how the MySQL Server and NDB handle table metadata, tables created or altered using the included MySQL server binary from NDB 8.0 cannot be restored using ndb_restore to NDB 7.6 or an earlier version of NDB Cluster. Such tables use .sdi files which are not understood by older versions of mysqld.

    A backup taken in NDB 8.0 of tables which were created in NDB 7.6 or earlier, and which have not been altered since upgrading to NDB 8.0, should be restorable to older versions of NDB Cluster.

    Since it is possible to restore metadata and table data separately, you can in such cases restore the table schemas from a dump made using mysqldump, or by executing the necessary CREATE TABLE statements manually, then import only the table data using ndb_restore with the --restore-data option.

  • Multi-threaded backups.  Multi-threaded backups taken in NDB 8.0 can be restored to an cluster running an earlier version of NDB in either of the following two ways:

  • Encrypted backups.  Encrypted backups created in NDB 8.0.22 and later cannot be restored using ndb_restore from NDB 8.0.21 or earlier.

  • NDB_STORED_USER privilege.  The NDB_STORED_USER privilege is supported only in NDB 8.0.

  • Maximum number of data nodes.  NDB Cluster 8.0 supports up to 144 data nodes, while earlier versions support a maximum of only 48 data nodes. See Section 5.23.2.1, “Restoring to Fewer Nodes Than the Original”, for information with situations in which this incompatibility causes an issue.