websphere Application serve node and nodegroup and nodeagent cells

Application servers, nodes, and cells:-

Application Servers:-

The application server is the primary runtime component in all configurations and is where an application actually executes. All WebSphere Application Server configurations can have one or more application servers. In the Express and Base configurations, each application server functions as a separate entity. There is no workload distribution or central administration among application servers. With Network Deployment, you can build a distributed server environment consisting of multiple application servers maintained from a central administration point. In a distributed server environment, you can cluster application servers for workload distribution.

Nodes, node groups, and node agents:-

A node is a grouping of application servers for configuration and operational management on one machine. Nodes are generally associated with a physical machine. It is possible to have multiple nodes on a single machine, but nodes cannot span machines. In a stand-alone application server environment, there is only one node. With Network Deployment, you can configure multiple nodes in a distributed server environment that are managed from one central administration server.

In centralized management configurations, each node has a node agent that works with the deployment manager to manage administration processes. The nodeagent is created under the covers when you federate a stand-alone node to a cell.

A node group is a grouping of nodes within a cell that have similar capabilities. A node group validates that the node is capable of performing certain functions.

Cells:-

A cell is a grouping of nodes into a single administrative domain. In the Base and Express configurations, a cell contains one node and that node contains one application server. 

In a distributed server configuration, a cell can consist of multiple nodes, which are all administered from a single point (the deployment manager). The configuration and application files for all nodes in the cell are centralized into a master configuration repository. This centralized repository is managed by the deployment manager and synchronized with local copies that are held on each of the nodes.

Federation:-

Federation is a kind of process to manage the deployment manager profile with either AppServer profile or Custom profile for administration. Once we add a node to the deployment manager we can create number of servers under that node. So, we can have a single point of administration and we can have a clustered environment. Without federation we cannot create the clusters. At the time of federation nodeagent will be created to communicate between deployment manager and the federated profile.

Servers:-

WebSphere Application Server supplies application servers, which provide the functions that are required to host applications and proxy servers that distribute work to the application servers. It also provides the ability to define external servers to the administration process.

Application servers provide the runtime environment for application code. They provide containers and services that specialize in enabling the execution of specific Java application components. Each application server runs in its own Java Virtual Machine (JVM).