One shortcoming of the PVFS1 system is its reliance on the socket networking interface and local file systems for data and metadata storage.
If we look at most cluster computers today we see a variety of networking technologies in place. IP, IB, Myrinet, and Quadrics are some of the more popular ones at the time of writing, but surely more will appear and disappear in the near future. As groups attempt to remotely access data at high data rates across the wide area, approaches such as reliable UDP protocols might become an important component of a parallel file system as well. Supporting multiple networking technologies, and supporting them efficiently is key.
Likewise many different storage technologies are now available. We're still getting our feet wet in this area, but it is clear that some flexibility on this front will pay off in terms of our ability to leverage new technologies as they appear. In the mean time we are certainly going to leverage database technologies for metadata storage – that just makes good sense.
In PVFS2 the Buffered Messaging Interface (BMI) and the Trove storage interface provide APIs to network and storage technologies respectively.