Hadoop and GFS are good examples and they work great for the
single distributed application that is *written* with them
in mind.
Unfortunately, I can not stretch my imagination hard enough
to see them as general purpose filesystems backing up data
for gazillions of non-cooperative applications. The sort
of thing NFS and AFS were built to accomplish.
I *think* the folks at google also use GFS for shared $HOME
(ie. to stash files they want to share with others). I
could be wrong.
Roman.
Tim Newsham
http://www.thenewsh.com/~newsham/