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homework-4

# homework-4 - four blocks on four disks stored on the fifth...

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CSE 421/521 – Operating Systems Fall 2011 - Homework Assignment #4 The due date is: December 6 th , Tuesday, before the class (9:30am). Late submission is not allowed. No soft copies, paper submission only! Problem 1: Consider a file system on a disk that has both logical and physical block sizes of 512 bytes. Assume that the information about each file is already in memory. For each of the three allocation strategies (contiguous, linked, and indexed), answer these questions: a. How is the logical-to-physical address mapping accomplished in this system? (For the indexed allocation, assume that a file is always less than 512 blocks long.) b. If we are currently at logical block 10 (the last block accessed was block 10) and want to access logical block 4, how many physical blocks must be read from the disk? Problem 2: Consider a RAID Level 5 organization comprising five disks, with the parity for sets of
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Unformatted text preview: four blocks on four disks stored on the fifth disk. How many blocks are accessed in order to perform the following? a. A write of one block of data b. A write of seven continuous blocks of data Problem 3: Consider a distributed system with two sites, A and B. Consider whether site A can distinguish among the following: a. B goes down. b. The link between A and B goes down. c. B is extremely overloaded and its response time is 100 times longer than normal. What implications does your answer have for recovery in distributed systems? Problem 4: Consider AFS, which is a stateful distributed file system. What actions need to be performed to recover from a server crash in order to preserve the consistency guaranteed by the system? Problem 5: Consider the centralized and the fully distributed approaches to deadlock detection. Compare the two algorithms in terms of message complexity....
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