With the development of Internet-based business, Web applications are becoming increasingly complex. The J2EE specification aims at enabling the design of such web application servers. These servers have to ensure scalability and availability of the supported applications. Scalibility can be achieved using replication techniques or partitionning techniques. The aim of this paper is to compare these approaches. In a J2EE web application server, one important component is the EJB tier. In this context, the JOnAS web application server provides an example of EJB replication system called CMI (Cluster Method Invocation). In a first step, this paper presents a performance evaluation of CMI. It then introduces incrementally an alternative scheme based on partitionning and shows the performance benefits compared to CMI. Categories and Subject Descriptors D.4.8 [Operating Systems]: Performance – Measurements, Monitors. General Terms Algorithms, Measurement, Performance, Design, Reliability,...