| As cluster-based Web servers are increasingly adopted to host a variety of network-based services, performance improvement of these servers has become a critical issue. Since user-level communication is an effective technique to reduce the intra-cluster communication overhead, cluster-based Web server design utilizing user-level communication mechanisms has been a popular research focus in recent times. In this context, the overall objective of this research is to explore several design issues in order to enhance the performance of cluster-based network servers based on user-level communication mechanisms.; Due to their complexity, the performance of cluster-based Web servers is dependent on various design choices and demands imposed on the systems. Therefore, we investigate several design issues with different system environments as explained below. First, we propose a coscheduled server model, which coschedules the communication processes of a request. Its main objective is to minimize the response time of requests that need intra-cluster communication. The coscheduled server is modeled using two known coscheduling techniques, called Dynamic Coscheduling (DCS) and DCS with immediate blocking. Second, we investigate the impact of the Secure Socket Layer (SSL) offering in cluster-based application servers and propose a SSL backend forwarding scheme, called SSL_with_bf . Although SSL is the most popular protocol to provide a secure channel between a client and an application server, its high overhead degrades the server performance considerably, and thus, affects the server scalability. Therefore, improving the performance of SSL-enabled application servers is critical for designing scalable and high performance data centers. Next, we propose a NIC data caching scheme, which uses the available NIC memory for caching recently accessed data blocks to improve the distributed Web server's performance. Although NIC memory is traditionally used for communication, it can be used for improving performance as well because modern NICs are equipped with much larger amounts of memory.; To investigate these techniques, we develop a comprehensive simulation testbed that captures the underlying communication layer in a cluster, the characteristics of various coscheduling algorithms, and the characteristics of a distributed Web server model. Extensive experiments of three proposed schemes using this testbed show that performance of cluster-based Web servers can significantly increase by employing these techniques. |
