CS 417 Exam 2
Fall 2005
Part I - 50 Points
- 9 points
Explain how cached data on the client is invalidated:
(a) in NFS.
(b) in AFS.
- 8 points
Explain the two methods available in ethernet cards for receiving select multicast
packets (rather than all multicast packets).
1.
2.
- 18 points
In a distributed shared memory system (DSM):
(a) How do you detect that your system is attempting to access a page that resides on another host?
(a) How do you determine which host has the page you need?
(a) Why may sequential consistency be undesirable in the implementation of a DSM system?
- 8 points
(a) Alice and Bob walked a mile from town when Bob realized that
he forgot to set his watch. Alice volunteers to walk back to town
to find the correct time from the clock tower. When she comes back,
a half-hour later, she tells Bob, "The time on the clock tower was
3:15." Using Cristians algorithm, to what time does Bob set his
watch?
(b) After Bob sets his watch, Alice confesses that she briefly
stopped to eat a doughnut when she was in town. Bob knows that Alice
walks at a relatively steady pace of three miles per hour. What
assumption can he make about the error of the time on his watch (±N
minutes)?
- 8 points
Explain two deficiencies with Lamport timestamps and how each can be rectified.
(a)
(b)
Part II - 50 Points
For each statement, select the most appropriate answer.
- The NFS automounter did not:
(a) eliminate the need to mount NFS resources; remote resources can be accessed directly via RPC.
(b) eliminate excessive delays due to NFS mounts during system boot.
(c) provide a mechanism to support replicated servers for read-only resources.
(d) allow clients to share a common namespace of NFS resources.
- Microsoft oplocks:
(a) improve file system performance by allowing clients to cache file data.
(b) allow a client to lock an entire file for exclusive access.
(c) allow a client to lock a byte-range of a file for exclusive access.
(d) enforce mutual exclusion for file access.
- Microsoft's SMB distributed file system architecture is most similar to:
(a) RPC access with sequential semantics.
(b) RPC access with session semantics.
(c) Upload/download access with sequential semantics.
(d) Upload/download access with session semantics.
- Which mutual exclusion algorithm does not rely on timestamps?
(a) Central-server.
(b) Ricart-Agrawala.
(c) Lamport.
(d) They all require timestamps.
- Which of the following is not suitable for group communication?
(a) Anycast.
(b) Multicast.
(c) Netcast.
(d) Broadcast.
- A persistent write-ahead log is important for:
(a) providing an audit trail.
(b) optimizing remote file system access.
(c) ensuring that a transaction remembers its state even upon reboot.
(d) allowing a client to play back file operations upon reconnection.
- A linear compensating function:
(a) speeds up or slows down the rate at which a clock ticks.
(b) adjusts a clock in steadily decreasing intervals until it asymptotically approaches the correct time.
(c) adds a constant offset to the value of the system clock.
(d) compensates for the irregularities of a quartz oscillator and ensures that the system clock ticks at a constant rate.
- At the end of the first phase of a two-phase commit protocol:
(a) all cohorts have received a request to commit from the coordinator.
(b) the coordinator received an acknowledgement to its request from all cohorts.
(c) all cohorts have received a commit or abort directive from the coordinator.
(d) the coordinator received all responses from cohorts to the commit or abort directive.
- When a replicated Coda file server is rebooted:
(a) it checks with other servers for updates.
(b) it waits for other servers to contact it with updates.
(c) it waits for a client to tell it that it has an old version of a file.
(d) it waits for the client to play back its client modification log.
- Which vector timestamp is concurrent with (1,0)?
(a) (0,0)
(b) (0,1)
(c) (1,1)
(d) All of the above.
