I've noticed that "cleaning up" in Time Machine seems to take two, three, more times as long as the actual backup. Since copying a single large file could take several seconds, while deleting one takes milliseconds, what sort of cleanup is actually happening?
Does it copy the files and then search for unchanged files to replace with hard links? That would be ridiculously inefficient.
One answer lists three things it does (which is the same as what I assumed it does) but doesn’t explain why it takes so long.
