Part 1: Receiver (Alice) sends existing file's fixed block hashes to sender (Bob):Īlice breaks-up lipsum.txt into equally sized blocks (for this demonstration lets use 32-byte sized blocks) and computes the weak hashes (checksums) of those blocks using the weak rolling hash of that block (note that the rolling-hash algorithm is not computed across block boundaries yet): block offset 32-byte block bytes (as ASCII) block weak-hash (as UInt32)Ġ |Lorem ipsum dolor sit amet, cons| 3262843843ġ6 |ectetur adipiscing elit. For this demonstration, the remote client ( Bob) is sending its modified copy of lipsum.txt to the rsync server ( Alice).
With rsync, it doesn't matter which host (computer) is running the server or client software, what matters is who the sender is and who the receiver is (as an rsync server can send and receive, and an rsync client can also send and receive). Malesuada pellentesque, ipsum sem porttitor est, quis laoreet urna orci a leo.Ĭras tincidunt porttitor sapien, quis cursus metus pulvinar id. Molestie nisl elit, suscipit egestas ex aliquam ac. Nulla ex metus, malesuadaĮget ultricies vel, fermentum quis nisl. MaurisĪliquam nisl nibh, sed tempus magna venenatis ac. Fusce iaculis libero vitae ipsum accumsan efficitur.įusce iaculis est et justo sollicitudin, sed porttitor augue sagittis. Nulla nisl enim, consectetur quis quam consequat, Lorem ipsum dolor sit amet,Ĭonsectetur adipiscing elit. Fusce sagittis vehicula ligula, necĪnd supposing a remote client ( Bob) has a slightly modified copy of lipsum.txt: Proin finibus ullamcorper ante sit amet egestas. Cras tincidunt porttitor sapien, quis cursus metus Donecĭignissim, mauris nec malesuada pellentesque, ipsum sem porttitor est, quis Curabitur molestie nisl elit, suscipit egestas ex aliquam ac. Mauris aliquam nisl nibh, sed tempus magna venenatisĪc. Fusce iaculis est et justo sollicitudin, sed Nulla nisl enim,Ĭonsectetur quis quam consequat, pharetra tempus enim. Line-wraps at column 80 have been added for readability, the line-breaks would not be present in the actual file) Lorem ipsum dolor sit amet, consectetur adipiscing elit. Supposing a fileserver ( Alice) has this file 641 byte: lipsum.txt: I note that human-readable-text files can have their sentance/paragraph structure extracted for domain-specific synchronization optimizations, we aren't doing that: as far as rsync and the rolling-hash algorithm is concerned, every file is an opaque binary blob without any structure) So I offer my own example, using Lorem Ipsum text as an example of the data being synchronized. (I'm working on a remote-synchronization problem myself right now, and gives a good answer but I found their example a tad confusing.
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