[Unison-hackers] Other synching configurations

[Jerry Haltom]

So Unison seems to work best (or perhaps at all) when using a Hub
layout... one box on the middle synching to the others.

I'm wondering why this is.

If I sync one replica with two other replicas which also synch between
themselves, should not each replica be aware of it's change state and
try to replay that change state against each other, perhaps resulting in
an attempt to delete a file that was already deleted by a replica, or
modify a file that was already modified by another replica. But what
problems would that cause?

In the case of deleting, nothing should happen... it's already gone.

In the case of modifying or adding, you'd still have to check for
conflicts. If the files were being modified to the same state they are
already in, it doesn't seem like an error conditition to me.

So why does Unison only work well in a hub layout?