Cox, RussJosephson, William2015-10-062001Cox, Russ and William Josephson. 2001. Communication Timestamps for File System Synchronization. Harvard Computer Science Group Technical Report TR-01-01.http://nrs.harvard.edu/urn-3:HUL.InstRepos:23017121The problem of detecting various kinds of update conflicts in file system synchronization following a network partition is well-known. All systems of which we are aware use the version vectors of Parker et al. These require O(R*F) storage space for F files shared among R replicas. We propose a number of different methods, the most space-efficient of which uses O(R*F) space in the worst case, but O(R+F) in the expected case. To gain experience with the various methods, we implemented a file synchronization tool called Tra. Based on this experience, we discuss the advantages and disadvantages of each particular method. Tra itself turns out to be useful for a variety of tasks, including home directory maintenance, operating system installation, and managing offline work. We discuss some of these uses.en-USResearch Paper or Report2015-10-06