Java Architecture tutorial

Common Architectures Scalability: Scalability is the ability to economically support the required quality of service as the load increases. Two types: Vertical and Horizontal Vertical: Achieved by adding capacity (memory, CPUs, etc.) to existing servers. Requires few to no changes to the architecture of a system. Increases: Capacity, Manageability Decreases: Reliability, Availability (single failure is more likely to lead to system failure) Vertical scalability is usually cheaper than horizontal scalability. J2EE supports vertical scaling because of automatic lifecycle management. Adding more capacity to a server allows it to manage more components (EJBs, etc.). Horizontal: Achieved by adding servers to the system. Increases the complexity of the system architecture. Increases: Reliability, Availability, Capacity, Performance (depends on load balancing), Flexibility Decreases: Manageability (more elements in the physical architecture) J2EE supports horizontal scaling because the container and server handle clustering and load balancing. Availability and reliability are obtained through scalability. Scalability affects capacity.