Abstract

As we approach nation-wide integration of computer systems, it is clear that file replication will play a key role, both to improve data availability in the face of failures, and to improve performance by locating data near where it will be used. We expect that future file systems will have an extensible, modular structure in which features such as replication can be "slipped in" as a transparent layer in a stackable layered architecture. We introduce the Ficus replicated file system for NFS and show how it is layered on top of existing file systems. The Ficus file system differs from previous file replication services in that it permits update during network partition if any copy of a file is accessible. File and directory updates are automatically propagated to accessible replicas. Conflicting updates to directories are detected and automatically repaired; conflicting updates to ordinary files are detected and reported to the owner. The frequency of communications outages rendering i...

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