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.





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