The tradition of striping data across I/O servers in round-robin fashion has been in place for quite some time, and it seems as good a default as any given no more information about how a file is going to be accessed. However, in many cases we do know more about how a file is going to be accessed. Applications have many opportunities to give the file system information about access patterns through various high-level interfaces. Armed with this information we can make informed decisions on how to better distribute data to match expected access patterns. More complicated systems could redistribute data to better match patterns that are seen in practice.
PVFS2 includes a modular system for adding new data distributions to the system and using these for new files. We're starting with the same old round-robin scheme that everyone is accustomed to, but we expect to see this mechanism used to better access multidimensional datasets. It might play a role in data redundancy as well.