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,stores 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, and strives to provide the highest degree of consistency attainable in the light of these objectives. Measurements from a prototype show that the performance cost of providing high availability in Coda is reasonable. Index Terms- Andrew, availability, caching, disconnected operation, distributed file system, performance, portable computers, scalability, server replication. I.

An algorithm is described which guarantees reliable storage of data in a distributed system, even when different portions of the data base, stored on separate machines, are updated as part of a single transaction. The algorithm is implemented by a hierarchy of rather simple abstractions, and it works properly regardless of crashes of the client or servers. Some care is taken to state precisely the assumptions about the physical components of the system (storage, processors and communication).

Abstract This paper is a survey of the current state of the art in the design and implementation of distributed file systems. It consists of four major parts: an overview of background material, case studies of a number of contemporary file systems, identification of key design techniques, and an examination of current research issues. The systems surveyed are Sun NFS, Apollo Domain, Andrew, IBM AIX DS, AT&T RFS, and Sprite. The coverage of background material includes a taxonomy of file system issues, a brief history of distributed file systems, and a summary of empirical research on file properties. A comprehensive bibliography forms an important of the paper. Copyright (C) 1988,1989 M. Satyanarayanan The author was supported in the writing of this paper by the National Science Foundation (Contract No. CCR-8657907), Defense Advanced Research Projects Agency (Order No. 4976, Contract F33615-84-K-1520) and the IBM Corporation (Faculty Development Award). The views and conclusions in t...

The Unify system is exploring scalable approaches for designing distributed multicomputers that support a shared memory paradigm. To achieve massive scalability, unify employs highly efficient communication protocols to support new weak consistency sharing models. In particular, Unify introduces the notion of spatial consistency and a non-standard memory type called sequential segments. The combination of out-of-order spatial consistency and sequential segments increases concurrency, reduces the need for synchronization, and allows the use of highly efficient non-atomic multicast protocols. Our experience shows that there is a logical and intuitive connection (mapping) between sequential segments and a wide variety of parallel and distributed applications that require support for shared information. Moreover, the use of sequential segments results in simplified code and efficiency comparable to that of optimized message passing systems. This research was supported in part by NSF Gra...

Coda is a file system for a large-scale distributed computing environment composed of Unix workstations. It pro- vides resiliency to server and network failures through the use of two distinct but complementary mechanisms. One mechanism, server replication,stores 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, and strives to provide the highest degree of consistency attainable in the light of these objectives. Measurements from a prototype show that the performance cost of providing high availability in Coda is reasonable. Index Terms- Andrew, availability, caching, disconnected operation, distributed file system, performance, portable computers, scalability, server replication. I. INTRODUCTION LOCATION-t...

Floor control in synchronous groupware is the problem of how, when, and why participants interact in a shared computing environment while working simultaneously on common tasks. This thesis contends that floor control is a broader problem in synchronous groupware than has been seen by previous approaches, which have relied on narrow interpretations of the problem, and advocates a view of floor control that takes into account the role of floor control not only in managing conflicts but also in structuring a group and its communications. This view is supported by a descriptive model of floor control, referred to as G/TS/PAC (Group/Turn System/Perceive--Act--Cycle), which represents floor control as a process of communicating detailed floor control intent among participants. It is derived from a social--psychological model of turn--taking in conversation and a model of human--machine interaction, and generalizes those models in the context of synchronous groupware. G/TS/PAC represents fl...

An algorithm is described which guarantees reliable storage of data in a distributed system, even when different portions of the data base, stored on separate machines, are updated as part of a single transaction. The algorithm is implemented by a hierarchy of rather simple abstractions, and it works properly regardless of crashes of the client or servers. Some care is taken to state precisely the assumptions about the physical components of the system (storage, processors and communication).