CS3283_quiz_10_sol - CS3283 Distributed Systems Mid-term...

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1 CS3283 Distributed Systems Mid-term Test (1 hr 10min) Semester A, 2010/11 Name: ________________________ Student ID: ________ _____ Answer ALL questions. Write your answers on the space provided. (Totally 58 marks) Please ensure that your handwritings are readable and grammatically correct. Otherwise, marks may be deducted. The presentation and organization of your answers will also be counted in marking. Question 1 (8 marks) You are asked to design a distributed application and the following two system architecture options (Figure 1) are proposed. Give your comments focusing on (a) scalability, (b) reliability, (c) consistency, and (d) performance of the two options, (i) and (ii). Give one to two sentences to explain your comment for each issue. Client Server DB users Server Cache (i) (ii) Figure 1: Two design options for a distributed application. (a) scalability (2 marks): (i) is more scalability since the processing is more distributed. Some requests are processed at the client side. (b) reliability (2 marks): similar. The failure of server (both (i) and (ii)) will make the whole system cannot operate. (c) consistency (2 marks): (i) requires a higher cost to maintain the cached objects. (d) performance (2 marks): (i) can provide a better performance since it supports local processing using cached objects.
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2 Question 2 (11 marks) (i) Briefly explain how protection is provided in a process. How protection can be achieved in a thread? (3 marks) Protection (process) => Protection is provided by the OS. A process cannot access the address space belonging to another process. No direct communication between processes. They can only communicate indirectly through the OS with the using of semaphores/monitor in using shared resources. Protection (thread) => The OS does not provide protection to the threads within the same process. Protection is the responsibility of the programmer in using share resources. (ii)
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This note was uploaded on 01/16/2011 for the course CS CS3283 taught by Professor Kylam during the Spring '10 term at City University of Hong Kong.

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CS3283_quiz_10_sol - CS3283 Distributed Systems Mid-term...

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