Operating Systems Homework 4

CS 372 Operating Systems

Homework 4: Distributed Systems

Due: Monday, April at 10am in class McKinley,
10:50am in CS homework box Witchel

(15 pts) Write Policies. Compare write back and write through policies on a uniprocessor using the following criteria:
1. Speed
2. Consistency
3. Fault tolerance
4. Complexity
Does your solution still apply in a distributed system? Why or why not?
(15 pts) Distributed System Design. Some of the issues we considered for designing distributed systems are: naming, remote file access, performance (caching), fault tolerance (server state), and replication.
Choose three of these, and describe a tradeoff or interaction with one or more of the other design criteria.
(10 pts) Distributed File Systems. Consider a distributed file system that does client caching using write through. The system caches individual blocks, rather than entire files. Can the client in this system have a cache consistency problem? If so, suggest two possible solution.
(15 pts) Happens Before Relationship.
Given the above relationships answer the following questions.
- true or false: q0 happens before r0
- true or false: r0 happens before p1
- true or false: p2 is concurrent with r1
- Is there a legal/consistent arrival order at process q for messages r2 and r3? If so, what is it?
(15 pts) Failure Recovery for Semaphores. The decentralized semaphore implementation described in class has n points of failure! Describe a failure recovery algorithm that keeps track the semaphore. Feel free to modify any of the failure recovery algorithms described in lecture or the book.
(15 pts) Two-Phase Commit. What happens in the two-phase commit algorithm if a client fails during the transaction?
(15 pts) Security. Define the terms and give one example of: authentication, integrity, and privacy. Then, give an example of a system which supports authentication and integrity, but not privacy. Give another example which supports integrity and privacy, but not authentication.