NAME: ____________________________________ (FIRST NAME FIRST) SCORE: ____
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COSC 6360 FINAL EXAMINATION DECEMBER 12, 2006
THIS EXAM IS CLOSED BOOK. YOU CAN HAVE ONE SHEET (I.E., TWO PAGES) OF NOTES.
1. Mark all properties that apply to the following distributed file systems (5 points per correct line)
Distributed file system NFS AFS Coda
Does not trust its clients X X
Allows clients to hoard files X
Supports diskless clients X
Uses callbacks X X
Has no equivalent to the UNIX close() operation X
Attempts to maintain single-copy consistency X
2. What are the two kinds of old file versions that Elephants lets you save and how does it select them?
(2×5 points)
¾ Recent versions of files: they are identified by their timestamps
¾ Landmark versions: Elephant picks the last version of each group of updates
3. What is the purpose of the i-node map of a log-structured file system? (5 points) Where is it stored?
(5 points) How can we retrieve it when the system reboots after a crash? (5 points)
4. What are the main advantage and main disadvantage of journaling file systems implementing
synchronous log writes? (2×5 points)
¾ Main advantage: They guarantee metadata update durability by immediately
recording all metadata updates on the log.
¾ Main disadvantage: They have a much lower throughput than (a) journaling file
systems using asynchronous log writes and (b) file systems uising soft updates.
5. What would be the main disadvantage of a log-structured file system having very small—say, 16
kilobyte—segments? (5 points)
Having very small segments would void all the benefits of log-structured file systems
as long sequential writes would become impossible.
