Effectiveness and limitations of secondary servers for wide-area distributed file systems

Since the effective bandwidth of a wide-area network varies depending on the destination, we have developed the Aria wide-area distributed file system, which improves performance by utilizing secondary servers. The secondary servers cache (in a nonnaive manner) some of the files received from the primary server and serve them to clients so that the performance of the file system is improved. This paper presents guidelines on where the secondary servers should be placed so that they effectively reduce the overhead of narrow-band connections in a wide-area network. Our experiments using a prototype implementation of Aria revealed that a secondary server is able to improve the performance unless the communication bandwidth between the primary server and the secondary server is more than about 40% of the bandwidth between the secondary server and the clients. © 2000 Scripta Technica, Syst Comp Jpn, 31(11): 31–40, 2000