Basic Concepts


WebSphere Application Server Network Deployment and clustering terminology

To effectively implement network deployment and clustering with Device Manager, you need to understand the following WebSphere Application Server Network Deployment terminology:
Application server
An application server extends the ability of an HTTP server to handle Web application requests, and allows a server to generate dynamic, customized responses to client requests.
A group of related nodes and their node agents constitute a cell. Administrators define the nodes that make up a cell according to criteria that is appropriate in their environment.
A cell contains a Deployment Manager from which all the administrative tasks for the nodes in that cell are handled. Deployment Manager for the cell has a master configuration repository that contains the configuration data for the nodes and servers within the cell. Configuration changes made at the cell level are propagated to the nodes and servers the next time synchronization occurs. Therefore, all configuration changes must be made at the cell level.
Although each node and server in a cell have their own local configuration files, configuration changes made at the node or server level are temporary and will be overlaid with the data from the cell repository maintained by the Deployment Manager.
Node and node agent
A node is a logical grouping of WebSphere Application Server managed server processes that share common configuration control. A node usually corresponds to a physical computer with a distinct IP address. A node is normally associated with one physical installation of WebSphere Application Server. The node name is typically identical to the host name of the computer.
A node contains one or more application servers, XML configuration files, and an activated node agent. The node agent communicates with the cell's Deployment Manager to manage that set of servers on the node.
Deployment Manager
Deployment Manager is a special application server which manages the configuration of multiple application servers across multiple nodes in a cell. Deployment Manager includes an Administrative Console for implementing the configuration management.
Deployment Manager is available with the Network Deployment edition of WebSphere Application Server.
A cluster is a logical collection of application server processes that are grouped together solely for the purpose of providing workload distribution and failover. Servers which are members of a cluster must all have identical application components deployed on them.
The servers that are members of a cluster can be on located on the same host computer and node, which is called vertical clustering, or on different host computers and nodes, which is called horizontal clustering.
A cluster is not the same as a cell. A WebSphere Application Server Network Deployment cell can have zero clusters, one cluster, or multiple clusters.
Edge Server Load Balancer
The load balancer distributes workload among HTTP servers in a cluster.