NAS and NFS
Well, this gets right into the sticky wicket. There are potential problems with UDP and relational databases as you describe. The question is how can a stateless protocol like UDP work with statefull processes like relational databases have? It seems to me like it's a little bit more than just a "mileage may vary" answer. I have not heard of anybody's database blowing up from using NAS and NFS, but that doesn't mean it can't happen. It's also one of the main reasons Network Appliance, for instance, is developing DAFS, so they can get guaranteed, in-order delivery of relational database file-level I/O.