Sprite is a new operating system for networked uniprocessor and multiprocessor workstations with large physical memories. It implements a set of kernel calls much like those of 4.3 BSD UNIX, with extensions to allow processes on the same workstation to share memory and to allow processes to migrate between workstations. The implementation of the Sprite kernel contains several interesting features, including a remote procedure call facility for communication between kernels, the use of prefix tables to implement a single file name space and to provide flexibility in administering the network file system, and large variable-size file caches on both client and server machines, which provide high performance even for diskless workstations.

Extensive caching is a key feature of the Echo distributed file system. Echo client machines maintain coherent caches of file and directory data and properties, with write-behind (delayed write-back) of all cached information. Echo specifies ordering constraints on this write-behind, enabling applications to store and maintain consistent data structures in the file system even when crashes or network faults prevent some writes from being completed. In this paper we describe the Echo cache's coherence and ordering semantics, show how they can improve the performance and consistency of applications, and explain how they are implemented. We also discuss the general problem of reliably notifying applications and users when write-behind is lost; we addressed this problem as part of the Echo design but did not find a fully satisfactory solution.

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...

Naming is an important aspect of distributed system design. A naming system allows users and programs to assign character-string names to objects and subsequently use the names to refer to those objects. With the interconnection of clusters of computers by wide-area networks and internetworks, the domain over which naming systems must function is growing to encompass the entire world. In this paper, we address the problem of a global naming system, proposing a three-level naming architecture that consists of global, administrational, and managerial naming mechanisms, each optimized to meet the performance, reliability, and security requirements at its own level. We focus in particular on a decentralized approach to the lower levels, in which naming is handled directly by the managers of the named objects. Client name caching and multicast are exploited to implement name mapping with almost optimum performance and fault tolerance. We also show how the naming system can be made...

of the Dissertation Roam: A Scalable Replication System for Mobile and Distributed Computing by David Howard Ratner Doctor of Philosophy in Computer Science University of California, Los Angeles, 1998 Professor Gerald J. Popek, Co-chair Professor W. W. Chu, Co-chair Mobile computing is rapidly becoming a way of life. Users carry their laptops, PDAs, and other portable devices with them almost constantly, whether their mobility takes them across town or across the world. Recent hardware innovations and improvements in chip technology have made mobile computing truly feasible. Unfortunately, unlike the hardware industry, much of today's system software is not "mobile-ready." Such is the case with the replication service. Nomadic users require replication to store copies of critical data on their mobile machines, since disconnected or poorly connected machines must rely primarily on local resources. However, the existing replication services are designed for stationary environments, a...

This paper introduces the Jade File System, which provides a uniform way to name and access files in an internet environment. Jade is a logical system that integrates a heterogeneous collection of existing file systems, where by heterogeneous we mean that the underlying file systems support different file access protocols. Because of autonomy, Jade is designed under the restriction that the underlying file systems may not be modified. In order to avoid the complexity of maintaining an internet-wide, global name space, Jade permits each user to define a private name space. Jade's name space supports two novel features: It allows multiple file systems to be mounted under one directory, and it permits one logical name space to mount other logical name spaces. A prototype of Jade has been implemented to examine and validate its design. The prototype consists of interfaces to the Unix File System, the Sun Network File System, and the File Transfer Protocol. This paper gives an overview of J...

This paper reports on the effectiveness of the caching strategy used in the Sprite network file system based on data taken over several weeks of day-to-day usage by a variety of users. Measurements include cache consistency activity, long term I/O traffic rates, long term cache hit rates, and the averages and variations in the size of the variable-sized caches. Network traffic is compared with traffic to the local cache, and the effects of paging traffic are con-sidered. The overall conclusion is that the caching system is quite effective and poses a low overhead. Using a delayed write strategy, 40 % to 50 % of the data written to client caches is never written through to a server, and less than 1 % of the open operations by clients resulted in cache consistency actions by a server. †

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This paper argues that a shared, distributed name space and I/O interface should be implemented inside the operating system kernel. The grounding for the argument is a comparison between the Sprite network operating system and the Mach microkernel. Sprite optimizes the common case of file and device access, both local and remote, by providing a kernel-level implementation. Sprite also allows for user-level extensibility by letting a user-level process implement the naming and I/O interfaces of the file system. Mach, in contrast, provide general interprocess communication and does not define a file system protocol in the kernel. [Published in the Proceedings of the 2nd USENIX Mach Symposium, Nov 20-22, 1991, pages 233250 ] 1 Introduction This paper argues that the file system is a mature enough abstraction that it should be implemented inside the operating system kernel for optimal performance. Data storage and high-level naming are fundamental features of today's computer syste...

We present the design, implementation, and evaluation of a fully distributed directory service for Farsite, a logically centralized file system that is physically implemented on a loosely coupled network of desktop computers. Prior to this work, the Farsite system included distributed mechanisms for file content but centralized mechanisms for file metadata. Our distributed directory service introduces tree-structured file identifiers that support dynamically partitioning metadata at arbitrary granularity, recursive path leases for scalably maintaining name-space consistency, and a protocol for consistently performing operations on files managed by separate machines. It also mitigates metadata hotspots via file-field leases and the new mechanism of disjunctive leases. We experimentally show that Farsite can dynamically partition file-system metadata while maintaining full file-system semantics. 1