Summary

The graph-based pervasive replication algorithms described in this section offer some fundamental benefits over traditional approaches that have a fixed set of servers manage replica locations.

Simple and efficient recovery from failures:

Graphs are, by definition, flexible--spanning edges to any replica makes the graph incrementally more robust and efficient. Moreover, using just one type of edges both to locate replicas and to propagate updates simplifies the recovery from permanent failures and avoids any system disruption during graph reconfiguration.

Decoupling of directories and files:

Directory entries point only to gold replicas, and the set of gold replicas is typically stable. Thus, a file and its parent directory act mostly independently once the file is created. Adding or removing a bronze replica for the file does not require a change to the directory replicas. Adding or removing a gold or bronze replica for the directory does not require a change to the file replicas. These are key properties for the system's efficiency.