CS550 Written Assignment 3 (WA#3)
• This is an individual assignment.
• Please upload your assignment on the Blackboard with the following name: Section_
LastName_FirstName_WA3.
• Please do NOT email your assignment to the instructor and TA!
Chapter 7
1. A file is replicated on 6 servers. List all the combinations of read quorum and write quorum that
are permitted by the voting algorithm.
2. What kind of consistency would you use to implement an electronic stock market? Explain your
answer？
3. Linearizability assumes the existence of a global clock. However, with strict consistency we
showed that such an assumption is not realistic for most distributed systems. Can linearizability
be implemented for physically distributed data stores?
Chapter 8
4. Suppose we have a system with 99.9996% availability, how much downtime a year can it have?
5. Write the reliability expression Rsystem(t) of the following series/parallel system, assuming that
each of the five modules has a reliability of R(t).
Chapter 9
6. Devise a simple authentication protocol using signatures in a public-key crypto-system.
7. How are ACLs implemented in a UNIX file system?
Chapter 11
8. Explain whether or not NFS is to be considered a distributed file system.
9. In UNIX-based operating systems, opening a file using a file handle can be done only in the
kernel. Give a possible implementation of an NFS file handle for a user-level NFS server for a
UNIX system.
10. Does NFS implement entry consistency?
