CSSE4004 - Lecture 6

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CSSE4004 - Lecture 6

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Question 1

Question
Which of the following is false about replication
Answer
  • good idea to ensure that all conflicting operations done in same order everywhere
  • guaranteeing global ordering on conflicting operations may be costly, downgrading scalability
  • replication can greatly increase performance of non-conflicting operations
  • Weakening consistency requirements to increases global synchronization requirements

Question 2

Question
Does this conform to sequential consistency?
Answer
  • True
  • False

Question 3

Question
Which of the following definitions are correct:
Answer
  • Read Your Writes: Effect of write operation by process on data item x, always seen by successive read operation on x by same process
  • Writes Follow Reads: Write operation by process on data item x following previous read operation on x by same process is guaranteed to take place on same or more recent value of x that was read.
  • Read write read: Write operation by process on data item x following previous read operation on x by same process is guaranteed to take place on same or more recent value of x that was read.
  • Read Your Writes: Write operation by process on data item x following previous read operation on x by same process is guaranteed to take place on same or more recent value of x that was read.

Question 4

Question
Which of the following is not a Data-Centric Consistency Model
Answer
  • Read-your-writes Consistency
  • Sequential Consistency
  • Causal Consistency
  • Eventual consistency

Question 5

Question
Which of the following is false about Object aware of replication
Answer
  • More difficult for developers
  • Allows for application specific solutions
  • Middleware handles communication
  • Middleware is responsible for ensuring objects are consistent across nodes

Question 6

Question
Which of the following is true about Monotonic reads and writes?
Answer
  • If process reads value of data item x, any successive read operation on x by that process will always return that same or more recent value
  • Write operation by process on data item x completed before any successive write on x by same process
  • If process reads value of data item x, any successive read operation on x by that process will always return a value no older than the latency between the client and the server
  • Write operation by process on data item x completed before any successive write by other users in the system

Question 7

Question
Does this conform to sequential consistency?
Answer
  • True
  • False

Question 8

Question
Does this conform to casual consistency?
Answer
  • True
  • False

Question 9

Question
Which of the following is not an advantage of replication?
Answer
  • Increase availability
  • Enhance reliability
  • Improve performance
  • Improved data consistency

Question 10

Question
Which of the following is false about eventual consistency?
Answer
  • Database must tolerate a high degree of inconsistency
  • Updates guaranteed to propagate to all replicas
  • if no updates for long time, all replicas gradually become consistent
  • Eventual consistency increases the time an insert operation takes

Question 11

Question
In Gifford's scheme, which of the following is true
Answer
  • To prevent read-write conflicts: Nr + Nw > N
  • To prevent write-write conflicts: Nw > N/2
  • To prevent read-write conflicts: Nw > N/2
  • To prevent write-write conflicts: Nr + Nw > N + 1

Question 12

Question
Which of the following is false about pull vs. push update protocols
Answer
  • Push: Server must have list of replicas
  • Push: No polling required
  • Pull: Updates are immediate
  • Pull: Polling required

Question 13

Question
Does this conform to casual consistency?
Answer
  • True
  • False

Question 14

Question
Does this conform to strict consistency?
Answer
  • True
  • False
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