File Synchronization with Vector Time Pairs

Vector time pairs are a new method for tracking syn- chronization metadata. A vector time pair consists of two vector times: one tracking file modification history and one tracking file synchronization history. Because the vector times are maintained separately and used for different purposes, different algorithms and optimizations can be applied to each. As a result, vector time pairs impose no restriction on synchronization patterns, never falsely detect conflicts, require no space to store deletion notices, require network bandwidth proportional only to the number of files changed, and support partial synchronizations. No other current synchronization method has all these properties. Results from an implementation of vector time pairs in a new user-level file synchronizer called Tra confirm the benefits of vector time pairs.