Open Source Distributed File Systems?

bertok asks: "I've noticed that even though most MS Windows services can be clustered to some extent, file shares can't! At first glance, DFS seems to be the solution, but it doesn't propagate locks, so it's useless in a typical office environment for sharing documents. How have others solved this problem in the past for Microsoft-centric networks? Exchange public folders? Oracle's IFS? Third party products?" Come to think of it, it's been a while since we last asked this question. Have the 2+ years made a difference?