1COSC 6360 FOURTH PROBLEM SET DUE NOVEMBER 13, 2013 1. Which are the main advantage and the main disadvantage of using soft updates compared to using journaling with synchronous log updates? a. Main advantage: _____________________________________________________________________ b. Main disadvantage: __________________________________________________________________ 2. Why must NFS client requests be both self-contained and idempotent? They must be self-contained because ______________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ They must be idempotent because ________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ 3. How can NFS safe asynchronous writes be used to implement close-to-open consistency? _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ 4. Which parameter of LBFS controls the average size of LBFS chunks? _______________________________________________________________________________________25. Consider a distributed file system implementing close-to-open consistency. Assuming that • Alice opens the file at 9:30 AM, modifies it, and closes it at 10:35 AM, • Bob opens the file at 10:00 AM, modifies it, and closes it at 10:25 AM, • Carol opens the file at 10:20 AM, modifies it, and closes it at 10:45 AM, Which of these three users would see his or her changes actually incorporated in the final version of the file? _______________________________________________________________________________________ 6. What is the main motivation for tailpacking? _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ 7. What is the main advantage of extent allocation? Why does it work best when combined with delayed allocation? _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ 8. What is the role of the e-node in the Blue files system? Would you consider making it bigger than it is now? Why? Why not? _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________
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