This section provides definitions of key terms used to describe MySQL Cluster Manager and its components in this manual and in other documentation relating to MySQL Cluster Manager and MySQL Cluster.
Cluster. A MySQL Cluster deployment. A cluster consists of a set of MySQL Cluster processes running on one or more hosts. A minimal cluster is usually considered to include one management node, two data nodes, and one SQL node. A typical production cluster may have one or two management nodes, several SQL nodes, and 4 or more data nodes. The exact numbers of data and SQL nodes can vary according to data size, type and rating of hardware used on the hosts, expected throughput, network characteristics, and other factors; the particulars are beyond the scope of this document, and you should consult MySQL Cluster NDB 6.1 - 7.1, for more specific information and guidelines.
A computer where one or more MySQL Cluster processes are run. In this context, we sometimes refer more specifically to a cluster host.
The number of cluster processes and number of cluster hosts may be, but are not necessarily, the same.
A computer where an instance of the MySQL Cluster Manager agent runs.
In order to run a MySQL Cluster using MySQL Cluster Manager, the MySQL Cluster Manager agent must be running on each host where cluster processes are to be run. In other words, when using MySQL Cluster Manager, all cluster hosts must also be MySQL Cluster Manager agent hosts (although the reverse is not necessarily true). Therefore, you should understand that anytime we use the term host, we are referring to a host computer in both of the senses just given.
Process. In the context of MySQL Cluster, a process (more specifically, a cluster process) is a MySQL Cluster node, of one of the following 3 types: management node (ndb_mgmd), data node (ndbd or ndbmtd), or SQL node (mysqld). For more information about these node types and their functions in a cluster, see MySQL Cluster Core Concepts, and MySQL Cluster Nodes, Node Groups, Replicas, and Partitions.
Package. A copy of the MySQL cluster software. This should include the binary executables needed to run the cluster processes of the desired types on a given host. The simplest way to make sure that this is done is to place a copy of the entire MySQL Cluster distribution on each computer that you intend to use as a cluster host.
Configuration attribute. A value whose setting affects cluster operations in a clearly defined and measurable way. When running MySQL Cluster manually, configuration is accomplished using cluster configuration parameters, MySQL server options, and MySQL system and status variables; MySQL Cluster Manager masks the differences between these, provides a unified view of them; see Configuration attributes, for more information.
Client. The MySQL Cluster Manager client is a software application that allows a user to connect to MySQL Cluster Manager and perform administrative tasks, such as (but not limited to): creating, starting, and stopping clusters; obtaining cluster and cluster process status reports; getting cluster configuration information and setting cluster configuration attributes.