Seamless Access to Decentralized Storage Services in Computational Grids via a Virtual File System

Abstract

This paper describes a novel technique for establishing a virtual file system that allows data to be transferred user-transparently and on-demand across computing and storage servers of a computational grid. Its implementation is based on extensions to the Network File System (NFS) that are encapsulated in software proxies. A key differentiator between this approach and previous work is the way in which file servers are partitioned: while conventional file systems share a single (logical) server across multiple users, the virtual file system employs multiple proxy servers that are created, customized and terminated dynamically, for the duration of a computing session, on a per-user basis. Furthermore, the solution does not require modifications to standard NFS clients and servers. The described approach has been deployed in the context of the PUNCH network-computing infrastructure, and is unique in its ability to integrate unmodified, interactive applications (even commercial ones) and existing computing infrastructure into a network computing environment. Experimental results show that: (1) the virtual file system performs well in comparison to native NFS in a local-area setup, with mean overheads of 1 and 18%, for the single-client execution of the Andrew benchmark in two representative computing environments, (2) the average overhead for eight clients can be reduced to within 1% of native NFS with the use of concurrent proxies, (3) the wide-area performance is within 1% of the local-area performance for a typical compute-intensive PUNCH application (SimpleScalar), while for the I/O-intensive application Andrew the wide-area performance is 5.5 times worse than the local-area performance.