UNIVERSITY OF HOUSTON Department of Computer Science COSC 6360--Operating Systems QUALIFYING EXAMINATION-Graduate Part FINAL EXAMINATION-Part II May 13, 1999 This exam is closed book. You can have two sheets (i.e., four pages) of notes. 1. File Systems: In opposite to what happened ten years ago, disk drive capacities are now increasing at a faster rate than main memory capacities. How should this evolution affect log- structured file systems (LFS)? What changes would you bring to improve their performance? (20 points) 2. Extending Remote Procedure Calls: How would you extend the remote procedure call model to let them handle C++ or Java style objects? The CORBA solution is quite interesting: while elementary data types such as integers, floating-point numbers and so forth continue to be passed by value, more complex objects are passed by reference, which forces the server to call back the client every time it wants to access any object. What are the advantages and disadvantages of this solution? Can you think of other possible approaches? What would be their advantages and disadvantages? (20 points) UNIVERSITY OF HOUSTON Department of Computer Science COSC 6360--Operating Systems FINAL EXAMINATION-Part I May 13, 1999 This exam is closed book. You can have two sheets (i.e., four pages) of notes. 1. Give your own example of an anomalous behavior in a distributed system using logical clocks. (5 points) Under which condition could this anomalous behavior still happen in a system using physical clocks. (5 points) 2. What needs to be done if the private key of the Kerberos ticket granting service (TGS) becomes known to one or more intruders? (10 points) 3. What makes the Bullet file system so fast? (5 points) What are the limitations of the approach (5 points) 4. What is the major motivation for AFS callbacks? (5 points) What is their major disadvantage and how does AFS solve that problem? ( 5 points) 5. What is a witness and what is their major advantage? (5 points) 6. Why does Grapevine assign by default several mailboxes to each individual user? (5 points) 7. Why did the designers of Sprite decide to use ordinary Sprite files as backing storage for their virtual memory system? (10 points)