A quantitative analysis of cache policies for scalable network file systems
01 May 1994-Vol. 22, Iss: 1, pp 150-160
TL;DR: In this paper, the authors investigated the quantitative performance effect of moving as many of the server responsibilities as possible to client workstations to reduce the need for high-performance server machines.
Abstract: Current network file system protocols rely heavily on a central server to coordinate file activity among client workstations This central server can become a bottleneck that limits scalability for environments with large numbers of clients In central server systems such as NFS and AFS, all client writes, cache misses, and coherence messages are handled by the server To keep up with this workload, expensive server machines are needed, configured with high-performance CPUs, memory systems, and I/O channels Since the server stores all data, it must be physically capable of connecting to many disks This reliance on a central server also makes current systems inappropriate for wide area network use where the network bandwidth to the server may be limitedIn this paper, we investigate the quantitative performance effect of moving as many of the server responsibilities as possible to client workstations to reduce the need for high-performance server machines We have devised a cache protocol in which all data reside on clients and all data transfers proceed directly from client to client The server is used only to coordinate these data transfers This protocol is being incorporated as part of our experimental file system, xFS We present results from a trace-driven simulation study of the protocol using traces from a 237 client NFS installation We find that the xFS protocol reduces server load by more than a factor of six compared to AFS without significantly affecting response time or file availability
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01 Dec 1995TL;DR: A new paradigm for network file system design, serverless network file systems that utilizes workstations cooperating as peers to provide all file system services to provide better performance and scalability than traditional file systems.
Abstract: In this paper, we propose a new paradigm for network file system design, serverless network file systems. While traditional network file systems rely on a central server machine, a serverless system utilizes workstations cooperating as peers to provide all file system services. Any machine in the system can store, cache, or control any block of data. Our approach uses this location independence, in combination with fast local area networks, to provide better performance and scalability than traditional file systems. Further, because any machine in the system can assume the responsibilities of a failed component, our serverless design also provides high availability via redundant data storage. To demonstrate our approach, we have implemented a prototype serverless network file system called xFS. Preliminary performance measurements suggest that our architecture achieves its goal of scalability. For instance, in a 32-node xFS system with 32 active clients, each client receives nearly as much read or write throughput as it would see if it were the only active client.
626Â citations
Proceedings Article•
18 Jun 2000TL;DR: This paper describes the collection and analysis of file system traces from a variety of different environments, including both UNIX and NT systems, clients and servers, and instructional and production systems and develops a new metric for measuring file lifetime that accounts for files that are never deleted.
Abstract: In this paper, we describe the collection and analysis of file system traces from a variety of different environments, including both UNIX and NT systems, clients and servers, and instructional and production systems. Our goal is to understand how modern workloads affect the ability of file systems to provide high performance to users. Because of the increasing gap between processor speed and disk latency, file system performance is largely determined by its disk behavior. Therefore we primarily focus on the disk I/O aspects of the traces. We find that more processes access files via the memory-map interface than through the read interface. However, because many processes memory-map a small set of files, these files are likely to be cached. We also find that file access has a bimodal distribution pattern: some files are written repeatedly without being read; other files are almost exclusively read. We develop a new metric for measuring file lifetime that accounts for files that are never deleted. Using this metric, we find that the average block lifetime for some workloads is significantly longer than the 30-second write delay used by many file systems. However, all workloads show lifetime locality: the same files tend to be overwritten multiple times.
507Â citations
14 Nov 1994
TL;DR: In this article, the authors examine four cooperative caching algorithms using a trace-driven simulation study and conclude that cooperative caching can significantly improve file system read response time and that relatively simple cooperative caching methods are sufficient to realize most of the potential performance gain.
Abstract: Emerging high-speed networks will allow machines to access remote data nearly as quickly as they can access local data. This trend motivates the use of cooperative caching: coordinating the file caches of many machines distributed on a LAN to form a more effective overall file cache. In this paper we examine four cooperative caching algorithms using a trace-driven simulation study. These simulations indicate that for the systems studied cooperative caching can halve the number of disk accesses, improving file system read response time by as much as 73%. Based on these simulations we conclude that cooperative caching can significantly improve file system read response time and that relatively simple cooperative caching algorithms are sufficient to realize most of the potential performance gain.
491Â citations
Proceedings Article•
25 Jun 2001
344Â citations
Proceedings Article•
22 Jan 1996TL;DR: Using trace-driven simulation, it is shown that a weak cache consistency protocol (the one used in the Alex ftp cache) reduces network bandwidth consumption and server load more than either time-to-live fields or an invalidation protocol and can be tuned to return stale data less than 5% of the time.
Abstract: The bandwidth demands of the World Wide Web continue to grow at a hyper-exponential rate. Given this rocketing growth, caching of web objects as a means to reduce network bandwidth consumption is likely to be a necessity in the very near future. Unfortunately, many Web caches do not satisfactorily maintain cache consistency. This paper presents a survey of contemporary cache consistency mechanisms in use on the Internet today and examines recent research in Web cache consistency. Using trace-driven simulation, we show that a weak cache consistency protocol (the one used in the Alex ftp cache) reduces network bandwidth consumption and server load more than either time-to-live fields or an invalidation protocol and can be tuned to return stale data less than 5% of the time.
342Â citations
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01 Dec 1989TL;DR: This best-selling title, considered for over a decade to be essential reading for every serious student and practitioner of computer design, has been updated throughout to address the most important trends facing computer designers today.
Abstract: This best-selling title, considered for over a decade to be essential reading for every serious student and practitioner of computer design, has been updated throughout to address the most important trends facing computer designers today. In this edition, the authors bring their trademark method of quantitative analysis not only to high-performance desktop machine design, but also to the design of embedded and server systems. They have illustrated their principles with designs from all three of these domains, including examples from consumer electronics, multimedia and Web technologies, and high-performance computing.
11,671Â citations
TL;DR: Observations of a prototype implementation are presented, changes in the areas of cache validation, server process structure, name translation, and low-level storage representation are motivated, and Andrews ability to scale gracefully is quantitatively demonstrated.
Abstract: The Andrew File System is a location-transparent distributed tile system that will eventually span more than 5000 workstations at Carnegie Mellon University. Large scale affects performance and complicates system operation. In this paper we present observations of a prototype implementation, motivate changes in the areas of cache validation, server process structure, name translation, and low-level storage representation, and quantitatively demonstrate Andrews ability to scale gracefully. We establish the importance of whole-file transfer and caching in Andrew by comparing its performance with that of Sun Microsystems NFS tile system. We also show how the aggregation of files into volumes improves the operability of the system.
1,604Â citations
TL;DR: This paper shows that disconnected operation is feasible, efficient and usable by describing its design and implementation in the Coda File System by showing that caching of data, now widely used for performance, can also be exploited to improve availability.
Abstract: Disconnected operation is a mode of operation that enables a client to continue accessing critical data during temporary failures of a shared data repository. An important, though not exclusive, application of disconnected operation is in supporting portable computers. In this paper, we show that disconnected operation is feasible, efficient and usable by describing its design and implementation in the Coda File System. The central idea behind our work is that caching of data, now widely used for performance, can also be exploited to improve availability.
1,214Â citations
Proceedings Article•
01 May 1999
TL;DR: In this paper, the authors describe disconnected operation in the Coda File System and show that disconnected operation is feasible, efficient and usable by describing its design and implementation in Coda file system.
Abstract: Disconnected operation is a mode of operation that enables a client to continue accessing critical data during temporary failures of a shared data repository. An important, though not exclusive, application of disconnected operation is in supporting portable computers. In this paper, we show that disconnected operation is feasible, efficient and usable by describing its design and implementation in the Coda File System. The central idea behind our work is that caching of data, now widely used for performance, can also be exploited to improve availability.
1,144Â citations
Book•
01 Dec 1988TL;DR: The Sun Network Fllesystem provides transparent, remote access to mesystems and uses an External Data Representation (XDR) specification to descnoe protocols in a machine and system independent way.
Abstract: The Sun Network Fllesystem (NFS) provides transparent, remote access to mesystems. Unlike many other remote rllesystem implementations under UNIXt, the NFS is designed to be easily portable to other operatin& systems and machine architectures. It uses an External Data Representation (XDR) specification to descnoe protocols in a machine and system independent way. The NFS is implemented on top of a Remote Procedure Call package (RPC) to help simplify protocol definition, implementation, and maintenance.
814Â citations