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Performance Evaluation of Computer Systems Part B Prof. G. Serazzi Dipartimento di Elettronica e Informazione Politecnico di Milano July 8, 2008 Name: ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... Family name: ... … … … … … … … … … … The Intranet of a medium scale company consists of three servers, namely A, B and C, which represent the web server of the clients, the application server and the database server, respectively. The intranet is modelled by an open queueing network. In order to evaluate the performance of the system a 10 minutes monitoring phase has been performed. The following data have been collected: CB Server B number of completions 150 CC Server C number of completions 300 C Network (intranet) completions 100 BB Server B busy time 300s BC Server C busy time 100s It is also known that the maximum throughput achievable by the intranet is 0.2 trans/sec. Compute: a) (1 pt) the service demands of all the servers and dete rmine the server which should be upgraded to achieve the maximum gain of the network performance b) (1 pt) the utilizations of all the servers c) (1 pt) the number of visits at server B d) (1 pt) the residence time of server A and the number of requests in A e) (3 pt) the minimum number of identical web servers to put in parallel such that the residence time at the web server layer is less than 18 seconds. Assume that incoming requests are uniformly distributed across the web servers. Consider the closed queueing network composed of servers A, B and C and a delay with Z=10s and the same service demands of the open queueing network without considering the servers added at point e). f) (2 pt) Represent the asymptotic bound X(N) and R(N) on system throughput and response time varying the population size N g) (2 pt) What…