two way mirroring or syncing?

[Kurt Granroth]

Does anybody know of a tool that will keep two directories totally in sync 
but not in real-time?  Basically, I want to have two directories /A and /B 
that every time they are synced (maybe once an hour), they will be 
identical.  Changes can happen on either /A or /B.

Now rsync is great for one-way updates.  If, say, all changes are only done 
to /A than rsync is perfect for keeping /B in sync.  However, if you start 
deleting files, then rsync doesn't know what to keep and what to delete.

Any ideas?
-- 
Kurt Granroth - "KDE -- Conquer Your Desktop"
KDE Developer/Evangelist | granroth@kde.org
http://www.granroth.org  | kurt@granroth.org