Varying WebSphere Application Server nodes without caching

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To determine the impact of using a WebSphere® Application Server cluster and varying the nodes without using caching, we ran several tests varying the nodes used in the cluster. The Trade database was defined on the DB2® UDB z/VM® guest and measurements were done varying the number of clients and setting the Trade caching mode to "No caching."

Figure 1. Varying WebSphere Application Server nodes without caching (transaction throughput)

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Observations

Figure 1 shows the behavior of a WebSphere Application Server cluster with one, two, and four WebSphere Application Server nodes. With two WebSphere Application Server nodes, the throughput increased significantly and drove the virtual CPU on the UDB server to its limit. Adding a second virtual CPU increased the throughput further and allowed additional clients to be served. With four WebSphere Application Server nodes we reached a throughput improvement of 70%.

Figure 2. Varying WebSphere Application Server nodes without caching (LPAR system load - eight physical CPUs)

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Observations

Figure 2 also shows that the virtual CPU utilization of the LPAR increased even further, up to 100%, meaning that the system was fully utilized.

Conclusions

If no caching is used, the environment could see a performance benefit from a four-node cluster by a throughput improvement of 70%. This requires a second virtual CPU for the DB2 UDB server. The throughput improvement is limited by the complete utilization of the eight CPUs of the LPAR.