Homework 12
Due 4/27/2012 [start of section]
Problem 1
What protocol would you use to guarantee that two web servers, one
in Boston and one in Austin, both start serving a new version of a
web site to clients at exactly the same time?
a. Two phase commit
b. Three phase commit or non-blocking commit
c. The FLP (Fisher Lynch Patterson) protocol
d. Leases
e. None of the above
Problem 2
What protocol would you use to move a subdirectory from one file server to another file server in the same machine room?
a. Two phase commit
b. Three phase commit or non-blocking commit
c. The FLP (Fisher Lynch Patterson) protocol
d. Leases
e. None of the above
Problem 3
In two-phase commit, suppose the master fails after writing
``GLOBAL_COMMIT'' to disk and sending ``GLOBAL_COMMIT'' to all
participating nodes but before any of the nodes receive this
message. Suppose that the ``GLOBAL_COMMIT'' message reaches i of
the n participants and that the participants implement a protocol
in which they communicate with one another when they suspect the
primary has died. What is the minimum number of participants that
must receive the ``GLOBAL_COMMIT'' message to allow the
participants to complete the transaction without waiting for the
master to recover?
Problem 4
In two-phase commit, suppose the master fails after writing
``GLOBAL_COMMIT'' to disk and sending ``GLOBAL_COMMIT'' to all
participating nodes but before any of the nodes receive this
message. Suppose that the ``GLOBAL_COMMIT'' message reaches i of
the n participants and that the participants implement a protocol
in which they communicate with one another when they suspect the
primary has died. What is the minimum number of participants that
must receive the ``GLOBAL_COMMIT'' message to allow the
participants to complete the transaction without waiting for the
master to recover?