A model of file server performance for a heterogeneous distributed system.

ABSTRACTIn this paper, we study the performance characteristics of a client-server style distributed system by a queueing network model. The system being modeled was based on an experimental distributed system currently being prototyped. As a specific detailed case study, we have evaluated the performance of a file server. A file server is a key component to achieve the data sharing necessary in a distributed system. The file server is probably the most heavily used resource of the distributed system and as a result, its performance is critical to the success of the system. The primary goal of the study was to identify and quantify the effects of the bottlenecks in the server and assess design alternatives to enhance performance. In particular, the improvements due to file caching, outboarding transport functions and the effect of multiple network interfaces were studied. We model in detail the various stages of processing of a request to a file server. Parameterization of the model was achieved by initial measurements made on the prototype system. An important characteristic modeled was the buffer overflow from the network interfaces. This required the approximate solution of a non-product-form queueing network.