Sun Java System Application Server Enterprise Edition 8.1 2005Q2 Deployment Planning Guide

Determining Which Topology to Use

To determine which topology (or variation) best meets your performance and availability requirements, test the topologies and experiment with different combinations of machines and CPUs.

Determine what trade-offs are required to meet your goals. For example, if ease of maintenance is critical, the separate tier topology is more suitable. The trade-off is that this topology requires more machines than the co-located topology.

An important factor in the choice of topology is the type of machines available. If the system contains large, Symmetric Multiprocessing (SMP) machines, the co-located topology is attractive because you can take full advantage of the processing power of these machines. If the system contains various types of machines, the separate tier topology can be more useful because you can allocate a different set of machines to the Application Server tier and to the HADB tier. For example, you might want to use the most powerful machines for the Application Server tier and less powerful machines for the HADB tier.

Comparison of Topologies

The following table compares the co-located topology and the separate tier topology. The left column lists the name of the topology, the middle column lists the advantages of the topology, and the right column lists the disadvantages of the topology

Table 3–1 Comparison of Topologies


Topology	Advantages	Disadvantages
Co-located Topology	Requires fewer machines. Because the HADB nodes and the Application Server instances are on the same tier, you are able to create an Application Server instance on each spare node to handle additional load. Improved CPU utilization. Processing is distributed evenly between an Application Server instance and an HADB node sharing one machine. Useful for large, Symmetric Multiprocessing (SMP) machines since it takes full advantage of their processing power.	Increased complexity of maintenance. For example, when you have to shut down machines hosting HADB nodes to perform maintenance, application server instances on the machine also become unavailable.
Separate Tier Topology	Easier maintenance. For example, you are able to perform maintenance on the machines that host Application Server instances without having to bring down HADB nodes. Useful with different types of machines. You are able to allocate a different set of machines to the Application Server tier and the HADB tier. For example, you are able to use more powerful machines for the Application Server tier and the less powerful machines for the HADB tier.	Requires more machines than the co-located topology. Because application server instances and HADB nodes are located on separate tiers, application server instances cannot be located on the machines that host the HADB spare nodes. Reduced CPU utilization. The application server tier and the HADB tier will likely have uneven loads. This is more significant with a small number of machines (four to six).