1. (5 points) From an NFS client, how many ``lookup'' calls are required to resolve the multi-part pathname of the following file that is stored on an NFS server? As with the rest of the questions, if you need more information to answer the question, you can make reasonable assumptions. Explain your answer.

          /nfs/users/csci555/midterm.questions
   

   
   
   

2. (10 points) Discuss the benefit of using the NFS Automounter in terms of performance and scalability.

   
   
   

3. (10 points) Considering the file systems we discussed during the classes (and listed above), is the cache consistency of a file guaranteed when the file server maintains state? Explain your answer with examples.

   
   
   

4. (10 points) Among the file systems we discussed during the classes (and listed above), which file system(s) would force an application programmer to use a separate file locking mechanism to guarantee the consistency of a file? Explain your answer.

Gifford's quorum consensus replication is in use at servers X, Y, and Z which all hold replicas of files A and B. The initial contents of all replicas of A are ``Advanced Operating Systems'' and B are ``CSci555''. The voting configuration for the replicas and read (r) and write (w) quorum sizes are listed on the table below. A client reads the value of A and then writes it to B.

1. (10 points) At the time the client performs these operations, a network partition separates servers X and Y from server Z. Describe the quora obtained and the operations that take place if the client can access servers X and Y.

   
   
   

2. (10 points) The partition still has not been repaired. Describe the quora obtained and the operations that take place if the client can access server Z only.

   
   
   

3. (10 points) The partition has been repaired and then another partition occured so that the servers Y and Z are separated from X. Describe the quora obtained and the operations that take place if the client can access the server X only.

In the November elections residents of Los Angeles will vote on a measure to split the city of Los Angeles, creating a smaller Los Angeles and two new cities, Hollywood, and San Fernando.

You have been hired by the city of Los Angeles to study the impact of the two secession ballot initiatives on the city's information technology department. While the City is hoping that it will not need to separate these services, it is your task to recommend changes to the design of information services in the city that will ease the transition (partition) of services in the event that ballot measures pass.

1. (10 points) Naming.
   Consider alternatives for naming documents or resources regarding parks, facilities, or other infrastructure provided by the city. Some alternatives includes, but are not limited to, global naming, host based naming, URL's (an instance of host based naming), various forms of centered naming, other forms of naming - including any variant you think is worth consideration.

   Discuss the benefits and drawbacks of these approaches considering normal operation (no secession), and the affect that secession will have on objects named with each approach.

   
   
   

2. (15 points) System design
   How would you architect the set of servers providing documents, supporting the naming of the objects, or supporting search of these documents. You goal is to simplify the transition to separate cities. If these services are to be run separately in the future, it will be necessary to divide both the equipment and the responsibilities handled by the equipment. It will be acceptable for the new cities to cooperate to some extent to ease the transition, or improve the reliability of each others systems.

   Consider techniques that could be used today to improve the performance and reliability of the systems, and explain how these techniques, if properly implemented, ease such a transition.

   
   
   

3. (10 points) Security
   Consider the identities of city residents and employees and how these identities might be managed by security systems that could be used in conjunction with both public access to city services and internal access by city employees. Consider how both the identities (how we refer to the principals) and the roles (what each can access) of these principals might change during secession. Discuss some of the security issues that might arise as a result of these changes.