UNIVERSITY OF HOUSTON Department of Computer Science COSC 6360-Operating Systems MIDTERM April 2, 1992 Be concise but complete. 1. What does Berkeley UNIX to protect its file systems against irrecoverable disk failures? (10 points) 2. What is an i-node? (5 points) How would you define i-nodes today if you had a chance to redesign the UNIX file system from scratch ? Justify your answer. (5 points) 3. (a) What is the difference between stream sockets and datagram sockets in Berkeley UNIX? (10 points). (b) Which ones are best suited to implement 1) a file transfer protocol such as ftp and 2) a name server? Justify both answers in a few words. (10 points) 4. In a recent paper, A. Tanenbaum argues that Mach is not a true distributed system because its message passing mechan- ism is optimized towards intra-host message passing. Is he factually true? (10 points) THIS QUESTION WAS RELATED TO A PAPER THAT IS NOT ANYMORE IN THE READING LIST. IT WILL BE NOT BE ASKED AGAIN. 5. How does the current Berkeley UNIX page replacement policy differs from that descibed by Babaoglu and Joy? (6 points) What factor motivated this change (4 points). 6. Sketch a modified MULTICS virtual memory architecture that would by handle much larger segments (say, one to four Giga- words)? What would be the impact of this change on the per- formance of the virtual memory? (20 points) THIS QUESTION WAS RELATED TO A PAPER THAT IS NOT ANYMORE IN THE READING LIST. IT WILL BE NOT BE ASKED AGAIN. 7. Briefly explain the positions of the two sides of the nested monitor call controversy (10 points). 8. How does the Cedar RPC implements complicated remote pro- cedure calls? (10 points)