We use the terms node and server interchangeably. Nodes are automatically grouped into regions, such that nodes within a region have low round-trip times (RTT) between them (5ms in our implementation). Pangaea uses region information to optimize replica placement and coordination.
Pangaea replicates data at the granularity of files and treats directories as files with special contents. Thus, we use the term file to refer to a regular file or a directory. An edge represents a known connection between two replicas of a file; updates to the file flow along edges. The replicas of a file and the edges between them comprise a strongly connected graph. The set of replicas of a file is called the file's replica set.