A new graphical reliability estimation tool, reliability Performance Module (RPM), is described. RPM combines the features of a powerful reliability tool, reliability Estimation System Testbed (REST), developed at NAS...
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A new graphical reliability estimation tool, reliability Performance Module (RPM), is described. RPM combines the features of a powerful reliability tool, reliability Estimation System Testbed (REST), developed at NASA Langley, with the convenient graphical modelling and simulation capabilities of an off-the-shelf commercial software package, Block Oriented Network Simulator (BONeS), from the Alta Group of Cadence Design systems. In order to estimate the reliability of a system, the built-in BONeS graphics capabilities are used to describe the system, and the embedded REST execution engine produces a reliability analysis automatically. An additional benefit of this approach is that a detailed failure modes and effects analysis can be derived by using the simulation capabilities of the tool. The usage of and output from RPM is demonstrated with an example system. As compared to our current design process, RPM promises to reduce overall modelling and analysis time, provide better documentation, make trade studies easier, create reusable modelling components and subsystems. and provide the integration of reliability and timing analysis necessary to guarantee the safety of critical real-time systems. Future work will concentrate on producing a more seamless integration of the reliability and timing analyses. Additional planned enhancements include a distributed (parallel) processing mode, and availability and phased-mission analysis capabilities.
In this paper, we present our approach to developing global picture archiving and communication system (PACS) remote consultation and diagnosis (RCD) application using the Open software Foundation (OSF) distributed Co...
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ISBN:
(纸本)0819417831
In this paper, we present our approach to developing global picture archiving and communication system (PACS) remote consultation and diagnosis (RCD) application using the Open software Foundation (OSF) distributed Computing Environment (DCE) services and toolkits. The current RCD system now uses programming services similar to those offered by OSF DCE, the Cell Directory Service, the distributed Time Service, the Security Service, the RPC Facility, and the Threads Facility. In this research we have formally applied OSF DCE services to the Global PACS RCD software. The use of OSF DCE services for Global PACS enables us to develop a robust distributed structure and new user services which feature reliability and scalability for Global PACS environments.
Although managing multiple copies of a database has been the subject of intensive research for quite some time now, it has yet to fulfill its promise in practical applications. In the current state of distributed data...
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Although managing multiple copies of a database has been the subject of intensive research for quite some time now, it has yet to fulfill its promise in practical applications. In the current state of distributeddatabase technology, data replication, if implemented at all, is typically enforced by the read-one-write-all protocol. More complicated but less restrictive replica control protocols, though a popular topic in research, are not implemented in any widely-used systems. A major reason for this lack of acceptance is that the performance impact of these protocols cannot be easily quantified, since very little existing performance figures of replicated commercial databasesystems.are available. This paper investigates the overhead of data replication, and compares the performance of a seldom implemented protocol, quorum consensus, with the performance of a widely accepted protocol, primary copy.
Simulation is a scientific method which is largely dominated by computers and has allowed the testing and assessment of many models before actual implementation. The paper proposes an approach to construction of a sim...
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Simulation is a scientific method which is largely dominated by computers and has allowed the testing and assessment of many models before actual implementation. The paper proposes an approach to construction of a simulation that models the behaviour of an adaptive queuing protocol (AQP). AQP was developed for database applications on mobile computers in a distributed multidatabase environment but can also be used in many other areas including distributed operating systems. By constructing the simulation model it is possible to both prove that it can be implemented, and at the same time study its expected behaviour in a mobile computing environment. The results of the simulation are analysed and discussed.< >
Research can rarely be performed on open platform based large scale distributedsystems.which always consist of heterogeneous sub-systems.and heterogeneous hardware and software components. It is not also pursued to r...
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Research can rarely be performed on open platform based large scale distributedsystems.which always consist of heterogeneous sub-systems.and heterogeneous hardware and software components. It is not also pursued to realize the integration of these sub-systems. highly reliable system operations and high productivity of application software development. Our solution is a Cooperating Autonomous Decentralized System Architecture which is an extendible concept of the conventional Autonomous Decentralized System Architecture. The new system architecture is a novel synthesis of four design principles: highly extensible addressing architecture, core communication protocols with minimal semantics, sophisticated network traffic control techniques and reliable communication control mechanism. The current implementation provides both flexibility and high reliability for integrating heterogeneous sub-systems. and it has been proven in several commercial systems.< >
The European Declarative System (EDS) is a high performance backend database server designed for a range of commercial mainframes. One major application domain of EDS is information processing for business and commerc...
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The European Declarative System (EDS) is a high performance backend database server designed for a range of commercial mainframes. One major application domain of EDS is information processing for business and commercial environments. High performance is achieved by exploiting parallelism using a shared-nothing computer (up to 256 processors). reliability is a crucial design issue for commercial and business information systems. Recovery control facilitates reliability and logging forms an important part of it. In general, logging is costly to implement. It is usually achieved at the expense of reduced system performance. Three logging schemes have been studied for EDS: (a) local discs-adopt a conventional approach by incorporating a local disc on each processor; (b) duplexing-arrange the processors in pairs, one for database operations and one for backup; and (c) cooperative logging-similar to duplexing except database and backup operations are performed on a single processor. The performance of these schemes for on-line transaction processing was evaluated and compared using the EDS behavioural simulator. The results of the evaluations are presented in this paper.
A new graphical reliability estimation tool, reliability Performance Module (RPM), is described. RPM combines the features of a powerful reliability tool, reliability Estimation System Testbed (REST), developed at NAS...
详细信息
A new graphical reliability estimation tool, reliability Performance Module (RPM), is described. RPM combines the features of a powerful reliability tool, reliability Estimation System Testbed (REST), developed at NASA Langley, with the convenient graphical modelling and simulation capabilities of an off-the-shelf commercial software package, Block Oriented Network Simulator (BONeS), from the Alta Group of Cadence Design systems. In order to estimate the reliability of a system, the built-in BONeS graphics capabilities are used to describe the system, and the embedded REST execution engine produces a reliability analysis automatically. An additional benefit of this approach is that a detailed failure modes and effects analysis can be derived by using the simulation capabilities of the tool. The usage of and output from RPM is demonstrated with an example system. As compared to our current design process, RPM promises to reduce overall modelling and analysis time, provide better documentation, make trade studies easier, create reusable modelling components and subsystems. and provide the integration of reliability and timing analysis necessary to guarantee the safety of critical real-time systems. Future work will concentrate on producing a more seamless integration of the reliability and timing analyses. Additional planned enhancements include a distributed (parallel) processing mode, and availability and phased-mission analysis capabilities.
We show an empirically driven process to validate the availability models of RISC System/6000 workstations. The empirical data is obtained by tracking RISC System/6000 workstations in the field. The tracking data is o...
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We show an empirically driven process to validate the availability models of RISC System/6000 workstations. The empirical data is obtained by tracking RISC System/6000 workstations in the field. The tracking data is obtained by using customer surveys and by using an availability measurement tool installed on selected running systems. We model several types of RISC System/6000 workstations using the SAVE tool. Care is taken to include all classes of systems. The workstations modeled include representatives from the desktop, deskside, and rack families. We explain the key principle of the "representative field model." For each type of workstation modeled, availability data for validation is extracted from the customer survey database or the availability measurement database. The validation data is used to identify and eliminate model errors. The identification and elimination of modeling errors involves sensitivity analysis. The validation of the availability measures of several RISC System/6000 workstations using both survey and measurement data confirms the accuracy of our modeling process and gives us the confidence to utilize the availability models in our development and marketing processes. Also, this enables us to generate accurate availability measures in our future availability modeling efforts.
Better data management is crucial to the success of scientific investigations of global change. New modes of research about the Earth, especially the synergistic interactions between observations and models, require m...
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Better data management is crucial to the success of scientific investigations of global change. New modes of research about the Earth, especially the synergistic interactions between observations and models, require massive amounts of diverse data to be stored, organized, accessed, distributed, visualized, and analyzed. To address technical issues of better data management, participants in Sequoia 2000, a collaborative effort between computer scientists and Earth scientists at several campuses of the University of California and at Digital Equipment Corporation (DEC), apply refinements in computing to specific applications. The software architecture includes layers for a common device interface, the file system, the database management system (DBMS), applications, and the network. Early prototype applications of this software include a global-change data schema, integration of a general circulation model (GCM), remote sensing, and a data system for climate studies. Longer range efforts include transfer protocols for moving elements of the database, controllers for secondary and tertiary storage, distributed file system, and a distributed DBMS.< >
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