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Integration of Adaptive file Assignment into distributed Safety-Critical systems

IFAC Proceedings Volumes 1996年第5期29卷 39-44页

作者： Horst F. Wedde Carsten Stange Jon A. Lind Informatik III University of Dortmund 44221 Dortmund / Germany

Safety-critical systems typically operate in unpredictable environments. Requirements for safety and reliability are in conflict with those for real-time responsiveness. Due to unpredictable environmental needs there is no static trade-off between measures to accommodate the conflicting objectives. Instead every feature or operating system service has to be adaptive.- The distributed operating system MELODY was developed for supporting safety-critical applications under such constraints. An essential adaptive feature in MELODY is its handling of distributed information resulting in strongly consistent (public) and weakly consistent (private) file copies, distributed over different system sites for both better availability and better reliability. Their number, location, and quality are adaptively rearranged to ensure system survivability under hard real-time constraints. The corresponding local managers are called file Assigners (FA). The paper describes their functionality. It focuses on their adaptive real-time integration into the task scheduler and file server operations. The quality of two different integration strategies (Task Scheduler and file Server oriented) has been evaluated through distributed experiments. Some experimental results are reported.

关键词： distributed Real-Time systems Operating systems distributed file systems Safety-Critical / Safety-critical systems Functional / Operational Integration

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DARB: A Dynamic Architecture for Data Replica Balancing

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CONCURRENCY AND COMPUTATION-PRACTICE & EXPERIENCE 2025年第9-11期37卷

作者： Fazul, Rhauani Weber Aita Mendizabal, Odorico Machado Barcelos, Patricia Pitthan Fed Univ Santa Catarina UFSC Postgrad Program Comp Sci Florianopolis SC Brazil Fed Univ Santa Maria UFSM Dept Languages & Comp Syst Santa Maria RS Brazil

distributed file systems, such as HDFS, are designed to support applications that handle large volumes of data. Data replication, which is at the core of the HDFS storage model, is essential for fault tolerance and performance. As new data are loaded into the system, the distribution of data blocks replicated among the nodes may become dissimilar affecting replica balancing and data locality. The HDFS Balancer is the official solution for redistributing the data already stored in the cluster. However, it overlooks the specific needs of the applications during data rearrangement and requires manual intervention by system administrators-a dependency that is often inadequate and inefficient. To address these limitations, this work presents DARB, a Dynamic Architecture for Replica Balancing that combines reactive and proactive strategies. The former uses the Prioritized Replica Balancing Policy to customize the replica balancing through configurable priorities. The latter consists of an event-driven strategy that makes the overall balancing process in HDFS transparent. DARB comprises modular components and a metrics observation model that identifies and determines when corrective actions should be taken. It also automatically triggers the HDFS Balancer based on standardized trigger events. The evaluation results reinforce that the proposed solution removes the need for manual configuration and execution while actively acting to keep the cluster balanced, taking into account performance, reliability, and data availability perspectives. Thus, DARB offers a sophisticated and specialized balancing solution that makes the balancing process seamless and flexible, introducing to the HDFS the concept of context-aware replica balancing.

关键词： balancing policy distributed file systems dynamic architecture fault tolerance replication trigger events

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Long term distributed file reference tracing: Implementation and experience

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SOFTWARE-PRACTICE & EXPERIENCE 1996年第6期26卷 705-736页

作者： Mummert, L Satyanarayanan, M School of Computer Science Carnegie Mellon University 5000 Forbes Avenue Pittsburgh PA 15213–3891 U.S.A. [*]School of Computer Science Carnegie Mellon University 5000 Forbes Avenue Pittsburgh PA 15213–3891 U.S.A.

DFSTrace is a system to collect and analyze long term file reference data in a distributed UNIX workstation environment, The design of DFSTrace is unique in that it pays particular attention to the efficiency, extensibility and the logistics of long-term trace data collection in a distributed environment. The components of DFSTrace are a set of kernel hooks, a kernel buffer mechanism, a data extraction agent, a set of collection servers and post-processing tools. Our experience with DFSTrace has been highly positive, Tracing has been virtually unnoticeable, degrading performance 3-7 per cent, depending on the level of detail of tracing. We have collected file reference traces from approximately 30 workstations continuously for over two years. We have implemented a post-processing library to provide a convenient programmer interface to the traces and have created an on-line database of results from a suite of analysis programs to aid trace selection. Our data has been used for a wide variety of purposes, including file system studies, performance measurement and tuning and debugging, Extensions of DFSTrace have enabled its use in applications such as field reliability testing and determining disk geometry. This paper presents the design, implementation and evaluation of DFSTrace and associated tools and describes how they have been used.

关键词： file reference tracing distributed file systems evaluation measurement

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FlexiFrag: A design pattern for flexible file sharing in distributed collaborative applications

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JOURNAL OF systems ARCHITECTURE 1998年第12期44卷 937-954页

作者： Pasala, A Ram, DJ Indian Inst Technol Dept Comp Sci & Engn Madras 600036 Tamil Nadu India

The need for flexible file sharing in distributed systems is increasing in applications such as calendar management, collaborative editing of documents, collaborative software developments etc. The file sharing policies required in these applications are often very different from the traditional read/write policies. Hence, a flexible way of specifying and implementing sharing policies on individual files in file systems is required. We propose a distributed object-based system model of constructing file systems. The object-based system model is based on a pattern called FlexiFrag. We show how a distributed object-based system and in particular distributed file system can be constructed using the pattern in a flexible way.

关键词： distributed file systems CSCW sharing policies design patterns calendar management

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THE INFLUENCE OF SCALE ON distributed file SYSTEM-DESIGN

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IEEE TRANSACTIONS ON SOFTWARE ENGINEERING 1992年第1期18卷 1-8页

作者： SATYANARAYANAN, M School of Computer Science Carnegie Mellon University Pittsburgh PA 15213

Scale should be recognized as a primary factor influencing the architecture and implementation of distributed systems. This paper uses Andrew and Coda, distributed file systems built at Carnegie Mellon University, to validate this proposition. Performance, operability, and security are dominant considerations in the design of these systems. Availability is a further consideration in the design of Coda. Client caching, bulk data transfer, token-based mutual authentication, and hierarchical organization of the protection domain have emerged as mechanisms that enhance scalability. The separation of concerns made possible by functional specialization has also proved valuable in scaling. Heterogeneity is an important by-product of growth, but the mechanisms available to cope with it are rudimentary. Physical separation of clients and servers turns out to be a critical requirement for scalability.

关键词： SCALABILITY distributed file systems ANDREW CODA SECURITY PERFORMANCE AVAILABILITY HETEROGENEITY REPLICATION CACHING LARGE-SCALE distributed systems DESIGN PRINCIPLES FOR SCALABILITY

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Survey of distributed file System Design Choices

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ACM TRANSACTIONS ON STORAGE 2022年第1期18卷 p4:1-4:34页

作者： Macko, Peter Hennessey, Jason NetApp Inc 1601 Trapelo Rd Waltham MA 02451 USA

Decades of research on distributed file systems and storage systems exists. New researchers and engineers have a lot of literature to study, but only a comparatively small number of high-level design choices are available when creating a distributed file system. And within each aspect of the system, typically several common approaches are used. So, rather than surveying distributed file systems, this article presents a survey of important design decisions and, within those decisions, the most commonly used options. It also presents a qualitative exploration of their tradeoffs. We include several relatively recent designs and their variations that illustrate other tradeoff choices in the design space, despite being underexplored. In doing so, we provide a primer on distributed file systems, and we also show areas that are overexplored and underexplored, in the hopes of inspiring new research.

关键词： distributed file systems distributed storage design options taxonomy survey

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IKAROS: An HTTP-Based distributed file System, for Low Consumption & Low Specification Devices

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JOURNAL OF GRID COMPUTING 2013年第4期11卷 681-698页

作者： Filippidis, Christos Cotronis, Yiannis Markou, Christos Univ Athens Dept Informat & Telecommun Athens Greece NCSR Demokritos Inst Nucl & Particle Phys Aghia Paraskevi Greece

We present the design of IKAROS: an HTTP-based distributed file system, which provides file access scalability and targets a large variety of operating systems and storage systems. IKAROS bypasses the server bottleneck enabling clients to access storage directly, while supporting the usage of multiple types of meta-data. It enables low-consumption, low-specification and low-cost devices to achieve a high throughput data transfer, responding to highly demanding applications. We present data transfer results comparing IKAROS, NFS, PVFS2 and HDFS on a Small Office/Home Office Network Attached Storage infrastructure. We show that IKAROS architecture satisfies and outperforms the data rate demands of high performance applications. We also present experimental results which compare IKAROS and GridFTP using the European Grid Infrastructure. IKAROS performs better in most cases while being competitive at the rest.

关键词： distributed file systems Low-technical specification storage units Low-power consumption Grid computing Network attached storage

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DESIGN AND IMPLEMENTATION OF A distributed file SYSTEM

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SOFTWARE-PRACTICE & EXPERIENCE 1991年第7期21卷 657-675页

作者： CHENG, HC SHEU, JP Department of Electrical Engineering National Central University Chung-Li 32054 Taiwan

We introduce a new model for replication in distributed systems. The primary motivation for replication lies in fault tolerance. Although there are different kinds of replication approaches, our model combines the advantages of modular redundancy and primary-stand-by approaches to give more flexibility with respect to system configuration. To implement such a model, we select the IBM PC-net with MS-DOS environment as our base. Transparency as well as fault-tolerance file access are the highlights of our system design. To fulfil these requirements, we incorporate the idea of directory-oriented replication and extended prefix tables in the system design. The implementation consists of a command shell, a DOS manager, and a recovery manager. Through this design, we can simulate a UNIX-like distributed file system whose function is compatible with MS-DOS.

关键词： CRASH RECOVERY distributed file systems file REPLICATION FAULT TOLERANCE NETWORK TRANSPARENCY

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Speculative execution in a distributed file system

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ACM TRANSACTIONS ON COMPUTER systems 2006年第4期24卷 361-392页

作者： Nightingale, Edmund B. Chen, Peter M. Flinn, Jason Univ Michigan Dept Elect Engn & Comp Sci Ann Arbor MI 48109 USA

Speculator provides Linux kernel support for speculative execution. It allows multiple processes to share speculative state by tracking causal dependencies propagated through interprocess communication. It guarantees correct execution by preventing speculative processes from externalizing output, for example, sending a network message or writing to the screen, until the speculations on which that output depends have proven to be correct. Speculator improves the performance of distributed file systems by masking I/O latency and increasing I/O throughput. Rather than block during a remote operation, a file system predicts the operation's result, then uses Speculator to checkpoint the state of the calling process and speculatively continue its execution based on the predicted result. If the prediction is correct, the checkpoint is discarded;if it is incorrect, the calling process is restored to the checkpoint, and the operation is retried. We have modified the client, server, and network protocol of two distributed file systems to use Speculator. For PostMark and Andrew-style benchmarks, speculative execution results in a factor of 2 performance improvement for NFS over local area networks and an order of magnitude improvement over wide area networks. For the same benchmarks, Speculator enables the Blue file System to provide the consistency of single-copy file semantics and the safety of synchronous I/O, yet still outperform current distributed file systems with weaker consistency and safety.

关键词： performance design distributed file systems speculative execution causality

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Achieving strong consistency in a distributed file system

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IEEE TRANSACTIONS ON SOFTWARE ENGINEERING 1997年第1期23卷 35-55页

作者： Triantafillou, P Neilson, C SIMON FRASER UNIV SCH COMP SCIBURNABYBC V5A 1S6CANADA

distributed file systems nowadays need to provide for fault tolerance. This is typically achieved with the replication of files. Existing approaches to the construction of replicated file systems sacrifice strong semantics (i.e., the guarantees the systems make to running computations when failures occur and/or files are accessed concurrently). This is done mainly for efficiency reasons. This paper puts forward a replicated file system protocol that enforces strong consistency semantics. Enforcing strong semantics allows for distributed systems to behave more like their centralized counterparts-an essential feature in order to provide the transparency that is so strived for in distributed computing systems. One fundamental characteristic of our protocol is its distributed nature. Because of it, the extra cost needed to ensure the stronger consistency is kept low since the bottleneck problem noticed in primary-copy systems is avoided, load balancing is facilitated, clients can choose physically close servers, and the work required during failure handling and recovery is reduced. Another characteristic is that instead of optimizing each operation type on its own, file system activity was viewed at the level of a file session and the costs of individual operations were able to be spread over the life of a file session. We have developed a prototype and compared the performance of the prototype to both NFS and a nonreplicated version of the prototype that also achieves strong consistency semantics. Through these comparisons the cost of replication and the cost of enforcing the strong consistency semantics are shown.

关键词： availability caching concurrency consistency semantics distributed file systems recovery replication

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