Integration of MySQL Cluster into MySQL Replication.  MySQL Cluster Replication makes it possible to replicate from one MySQL Cluster to another. Updates on any SQL node (MySQL server) in the cluster acting as the master are replicated to the slave cluster; the state of the slave side remains consistent with the cluster acting as the master. This is sometimes referred to as asynchronous replication between clusters, providing geographic redundancy. It is also possible to replicate from a MySQL Cluster acting as the master to a standalone MySQL server acting as the slave, or from a standalone MySQL master server to to a slave cluster; in either of these cases, the standalone MySQL server uses a storage engine other than NDBCLUSTER. Multi-master replication setups such as circular replication are also supported.

See Section 17.6, “MySQL Cluster Replication”.

Support for storage of rows on disk.  Storage of NDBCLUSTER table data on disk is now supported. Indexed columns, including the primary key hash index, must still be stored in RAM; however, all other columns can be stored on disk.

See Section 17.5.10, “MySQL Cluster Disk Data Tables”.

Variable-size columns.  In MySQL 5.0, an NDBCLUSTER table column defined as VARCHAR(255) used 260 bytes of storage independent of what was stored in any particular record. In MySQL 5.1 Cluster tables, only the portion of the column actually taken up by the record is stored. This makes possible a significant reduction in space requirements for such columns as compared to previous release series — by a factor of up to 5 in many cases.

User-defined partitioning.  Users can define partitions based on columns that are part of the primary key. It is possible to partition NDB tables based on KEY and LINEAR KEY schemes. This feature is also available for many other MySQL storage engines, which support additional partitioning types that are not available with NDBCLUSTER tables.

For additional general information about user-defined partitioning in MySQL 5.1, see Chapter 18, Partitioning. Specifics of partitioning types are discussed in Section 18.2, “Partition Types”.

The MySQL Server can also determine whether it is possible to “prune away” some of the partitions from the WHERE clause, which can greatly speed up some queries. See Section 18.4, “Partition Pruning”, for information about designing tables and queries to take advantage of partition pruning.

Autodiscovery of table schema changes.  In MySQL 5.0, it was necessary to issue a FLUSH TABLES statement or a “dummy” SELECT in order for new NDBCLUSTER tables or changes made to schemas of existing NDBCLUSTER tables on one SQL node to be visible on the cluster's other SQL nodes. In MySQL 5.1, this is no longer necessary; new Cluster tables and changes in the definitions of existing NDBCLUSTER tables made on one SQL node are immediately visible to all SQL nodes connected to the cluster.

Distribution awareness (NDB API).  Distribution awareness is a mechanism by which the best data node is automatically selected to be queried for information. (Conceptually, it is similar in some ways to partition pruning (see Section 18.4, “Partition Pruning”). To take advantage of distribution awareness, you should do the following:

Following these steps causes records with the same value for the partitioning column to be stored on the same partition (that is, in the same node group). When reading data, transactions are begun on the data node actually having the desired rows instead of this node being determined by the usual round-robin mechanism.

Using distribution awareness can yield performance increase of as great as 45% when using four data nodes, and possibly more when using a greater number of data nodes.