PDL Abstract

Replication Policies for Layered Clustering of NFS Servers

Proceedings 13th Annual Meeting of the IEEE International Symposium on Modeling, Analysis, and Simulation of Computer and Telecommunication Systems (MASCOTS). September 26 - 29, Atlanta, GA.

Raja R. Sambasivan, Andrew J. Klosterman, Gregory R. Ganger

Electrical and Computer Engineering
Carnegie Mellon University
Pittsburgh, PA 15213

Layered clustering offers cluster-like load balancing for unmodified NFS or CIFS servers. Read requests sent to a busy server can be offloaded to other servers holding replicas of the accessed files. This paper explores a key design question for this approach: which files should be replicated? We find that the popular policy of replicating readonly files offers little benefit. A policy that replicates readonly portions of read-mostly files, however, implicitly coordinates with client cache invalidations and thereby allows almost all read operations to be offloaded. In a read-heavy trace, 75% of all operations and 52% of all data transfers can be offloaded.