MySQL Cluster Architecture

MySQL Cluster is a high availability database which leverages a shared-nothing data storage architecture. The system consists of multiple nodes which can be distributed across hosts to ensure continuous availability in the event of a data node, hardware or network failure. MySQL Cluster Carrier Grade Edition uses a storage engine, consisting of a set of data nodes to store data, which is accessed through a native C++ API, Java, LDAP or standard SQL interface.

The MySQL Cluster architecture delivers carrier-grade availability and performance, without the traditional carrier-grade price

Identifying Optimal Applications for MySQL Cluster

Applications taking advantage of MySQL Cluster are characterized by requiring:

• 99.999% availability with sub-second failover and automatic recovery to minimize both planned and unplanned downtime.
• Extreme levels of real-time read / write performance with predictable, ultra-low latency response times.
• Dynamic scalability to meet the most unpredictable volumes of users and transactions.
• Mainly primary key access, or sub-components of a multi-field primary key
• Simple table joins
• Database size less than 2TB

MySQL Cluster Node Types

MySQL Cluster consists of three different types of nodes, each providing specialized services within the cluster.

Data Nodes are the main nodes of the cluster, providing the following functionality:

• Data storage and management of both in-memory and disk-based data
• Automatic and user defined partitioning of data, even as new nodes are added to a running cluster
• Synchronous replication of data between data nodes
• Transactions and data retrieval
• Automatic fail over
• Resynchronization after failure

By storing and distributing data in a shared-nothing architecture, i.e. without the use of a shared-disk, if a Data Node happens to fail, there will always at least one additional Data Node storing the same information. This allows for requests and transactions to continue to be satisfied without interruption. Data Nodes can also be added on-line, allowing for unprecedented scalability of data capacity and processing.

Application Nodes are the applications connecting to the database. This can take the form of an application leveraging the high performance NDB API or the use of MySQL Servers which perform the function of SQL interfaces into the data stored within a cluster. Thus, applications can simultaneously access the data in MySQL Cluster using a rich set of interfaces, such as SQL, LDAP and web services. Moreover, additional Application Nodes can be added online.

Management Nodes are responsible for managing the cluster and make cluster configuration information available to other nodes. The Management Nodes are used at startup and when there is a system reconfiguration. Management Nodes can be stopped and restarted without affecting the ongoing execution of the Data and Application Nodes. By default, the Management Nodes also provides arbitration services, in the event of a network failure leading to a "split-brain", or a cluster exhibiting "network-partitioning".

With this distributed architecture, where dependencies have been minimized, applications continue to run and data remains consistent, even if any one of the Data, Application, or Management Nodes fail.