Transactional file systems have been implemented to provide
stronger protection for application programs. Show a possible
interface and describe the semantics of a transactional file
system that buffers operational results till committed.
What issues should be addressed to ensure consistency across
machine crashes?
Suggest two situations in the two phase commit protocol in
which all the workers voted yes in the first phase, yet the
coordinator decides to abort the transaction.
A server manages the data items
a1, a2...an.
The server provides read and write operations on these items.
Consider the following transactions:
T
x = read(i); write(j,44);
U
write(i,55); write(j,66);
V
write(k,77); write(k,88);
Describe the information written to the log file if strict two
phase locking is in use, and U acquires ai and aj
before T. Describe how the recovery manager would uses this
information to recover the effects of T, U and V when the server
restarts after a crash. What is the significance of the commit
entries in a log file.
Five replicas A, B, C, D and E use quorum consensus with
weights A = 3, B = C = 2, D = E = 1. State the possible values
that may be chosen for a write quorum, Which choices allow the
service to continue when one of the servers is unavailable? Give
the choice of read quorums for each write quorum, and for each
read quorum, how may the quorum be formed and what is the minimum
number of servers involved?
