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 25.5.23.2.1, “Restoring to Fewer Nodes Than the Original”, for information with situations in which this incompatibility causes an issue.

When restoring the metadata from a backup (--restore-meta option), ndb_restore normally attempts to reproduce the captured table schema exactly as it was when the backup was taken.

Tables created in versions of NDB prior to 8.0 use .frm files for their metadata. These files can be read by the mysqld in NDB 8.0, which can use the information contained therein to create the .sdi files used by the MySQL data dictionary in later versions.

When restoring an older backup to a newer version of NDB, it may not be possible to take advantage of newer features such as hashmap partitioning, greater number of hashmap buckets, read backup, and different partitioning layouts. For this reason, it may be preferable to restore older schemas using mysqldump and the mysql client, which allows NDB to make use of the new schema features.

Tables using the old temporal types which did not support fractional seconds (used prior to MySQL 5.6.4 and NDB 7.3.31) cannot be restored to NDB 8.0 using ndb_restore. You can check such tables using CHECK TABLE, and then upgrade them to the newer temporal column format, if necessary, using REPAIR TABLE in the mysql client; this must be done prior to taking the backup. See Section 3.6, “Preparing Your Installation for Upgrade”, for more information.

You also restore such tables using a dump created with mysqldump.

Distributed grant tables created in NDB 7.6 and earlier are not supported in NDB 8.0. Such tables can be restored to an NDB 8.0 cluster, but they have no effect on access control.