Object-oriented framework for adaptation in a DFS

Today's large diversity of network resources, computing resources and heterogeneous devices can lead to a mismatch between network-capacity and the volume of data transferred, or between devices and data (consider transferring a large video clip to a handheld over a congested wireless network). Traditional distributed file systems including NFS [1], AFS [2] and Coda [3], fail to address this issue, as they cannot adapt their services according to environmental constraints. We address the problem of adaptation in a DFS by modeling the file system as an object-oriented framework using persistent distributed objects. Files (persistent objects) in the DFS participate when the system reacts to environmental constraints (e.g. network congestion) and/or user-imposed constraints (e.g. security). For instance, when the user wants to play a video clip stored on a remote server with an untrusted network in between, the system chooses a version of the clip appropriate to the current network traffic, encrypts it over the wire, and plays it on the client. Further, the behavior of our general-purpose framework can also be specialized according to specific application requirements, to implement domain-specific optimizations (e.g. modifying concurrent-write semantics).