Traditionally (and even now in most unices) hard links to directories were not allowed, in order to prevent endless recursive cases. Apple added the feature to

Traditionally (and even now in most unices) hard links to directories were not allowed, in order to prevent endless recursive cases. Apple added the feature to HFS+ in 10.5 so that Time Machine could make use of the optimization you describe. There are rules about directory hard links so that pathological recursion still cannot happen: http://lists.apple.com/archives/darwin-dev/2007/Dec/msg00029.html http://lists.apple.com/archives/darwin-dev/2007/Dec/msg00029...