I often replace files on my disk, and I also synchronize those files to a back-up disk.
I noticed that when I move a folder with, say, 300 large files in it, the synchronization process will re-copy those and also delete the 300 originals from the destination storage. This is sort of expected. But it can't be that difficult to optimize the process of synchronization by simply comparing let's say the "to copy" and "to delete" list, and when equal (based on the demanded criteria, such as name and/or size and/or timestamp etc), simply move corresponding files directly at the targeted destination, rather than deleting those and copy them again from source to destination.
Really? But I do use size already as a criterium. Maybe my impression was wrong. In fact, in a way, sync should perhaps always use the strictest criteria in an attempt to make it as performant as possible - regardless the demanded parameters. But I will verify this again, and perhaps add criteria just to be sure it works that way. Thanks for the info.
If you think it's making the wrong choice for a pair of files, open the Properties dialog for both of them (before carrying out any change that modifies either file) and check the size and date are exactly the same.