Coda: A Highly Available File System for a Distributed
Workstation Environment
M. Satyanarayanan
September 1989
Abstract
Coda is a file system for a large-scale distributed computing environment
composed of Unix workstations. It provides resiliency to server and network
failures through the use of two distinct but complementary mechanisms.
One mechanism, server replication involves storing copies of a file
at multiple servers. The other mechanism, disconnected operation,
is a mode of execution in which a caching site temporarily assumes the
role of a replication site. Disconnected operation is particularly useful
for supporting portable workstations. The design of Coda optimizes for
availability and performance, but provides the highest degree of consistency
attainable in the light of those objectives. Measurements from a prototype
show that the performance cost of providing high availability in Coda is
reasonable.