This is just a "I feel curious" question. When syncing locally (that is, from one drive to another on the same host), how does rsync know which files are not worth transmitting? I guess it does not do a full file compare (since that would be too expensive). Does it only do simple checking, like:
- file size
- modification time
If so, I guess it would be easy to fool rsync by changing the contents of the file, keeping the size, and resetting the modification time (if at all possible).