Harp: You do not have to worry about the details of view changes in Harp for now.  View changes are needed to 
switch to a new primary should the old one fail.  We will discuss them in detail in the next class.


Harp has many log pointers (FP, CP, AP, LB, GLB)
Why the FP-CP gap? (Hint: Does primary wait for ACKs from each backup before sending next operation to backups? Why?)
Why the CP-AP gap? (i.e. Why not apply to disk at CP?)
Why the AP-LB gap?
What is the LB? How does Harp find out what the current LB is?
Why the LB-GLB gap? (i.e. why not delete log record when disk write completes?)