InfoCenter Home > 7.1.3.2: Multi-tiered system sample topologyOverviewMulti-tiered topologies locate the Web server and application server processes on separate physical machines.An additional tier can contain databases, enterprise information systems, and other types of persistent storage. The following illustration shows an example of this type of topology. In this example, the application server processes that run a servlet are closer in network terms to the HTTP server, improving their response to client requests. The application server processes that run enterprise beans (Machine C) are closer in network terms to the application data, which is represented in an application by entity beans and stored on the database server (Machine D). An administrative server process is running on the two application server nodes. Application servers are cloned on Machine B and Machine C to help maximize the use of each machine's resources. (Two clones of each are shown in the example, but depending on the machine's hardware setup, more can potentially be added.) Typical useThe clones in a multi-tiered topology provide process redundancy and enable memory to be used more efficiently than in similar topologies that host only single instances of application servers. The additional resources that are available on the machines in this topology can improve the application's throughput and performance. If firewalls are introduced between the three application tiers, the same level of security can be provided for the entity beans in the application server as for the application data. Implementing a multi-tiered toplogy eliminates the local Java Virtual Machine (JVM) optimizations that occur when both the servlet engine and EJB server run in the same application server. It also introduces network latency. Both of these factors tend to slow down system performance. Although they provide more redundancy for application server processes, multi-tiered topologies also introduce more possible points of failure. The level of redundancy can make maintenance more complicated. |
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