Hah! NFS has a long and invidious history of (ahem) being a tad
optimistic about what exactly has made it to disk just yet...
Do _not_ trust NFS with database I/O is a fine maxim to work by.
Well, there's a little Database company called Oracle that disagrees
now. See, i.e.,
http://www.oracle.com/corporate/pressroom/html/oow_netw.html
Oracle is now convinced that, with the right implementation, the
likelihood of overoptimism via NFS is exactly equal with the likelihood of
overoptimism via a locally attached disk.