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Performance Evaluation of Computer Systems Part B Prof. G. Serazzi Dipartimento di Elettronica e Informazione Politecnico di Milano February 12, 2008 Name: ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... Family name: ... … … … … … … … … … … The Intranet of a medium scale company consists of three servers, namely A, B and C, which represent the web browser of the clients, the application server a nd 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: CA Server A number of completions 500 CB Server B number of completions 150 CC Server C number of completions 300 C Network (intranet) completions 75 BA Server A busy time 450s BB Server B busy time 300s BC Server C busy time 100s Compute: a) the utilizations of all the servers b) the service demands of all the servers, determine which is the bottleneck c) the number of visits at server A d) the service time at server A e) the arrival rate that saturates the system f) the response time of server A and the number of requests in A 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. g) Represent the asymptotic bound X(N) and R(N) on system throughput and response time varying the population size N h) Determine the minimum number of requests N such th at after this value the system is in the heavy load condition. i) Assume that the system works in the heavy lo ad condition. What is the maximum and minimum system response time? j) Compute the exact value of system throughput and response time when it is N=3. Solutions: 1) Ua=…