The following are limitations specific to the
NDB storage engine:
Machine architecture. All machines used in the cluster must have the same architecture. That is, all machines hosting nodes must be either big-endian or little-endian, and you cannot use a mixture of both. For example, you cannot have a management node running on a PowerPC which directs a data node that is running on an x86 machine. This restriction does not apply to machines simply running mysql or other clients that may be accessing the cluster's SQL nodes.
Schema operations. Schema operations (DDL statements) are rejected while any data node restarts. Schema operations are also not supported while performing an online upgrade or downgrade.
Number of fragment replicas. The number of fragment replicas, as determined by the
NoOfReplicasdata node configuration parameter, is the number of copies of all data stored by NDB Cluster. Setting this parameter to 1 means there is only a single copy; in this case, no redundancy is provided, and the loss of a data node entails loss of data. To guarantee redundancy, and thus preservation of data even if a data node fails, set this parameter to 2, which is the default and recommended value in production.
NoOfReplicasto a value greater than 2 is possible (to a maximum of 4) but unnecessary to guard against loss of data. In addition, values greater than 2 for this parameter are not supported in production.