Manufacturing flow line systems: a review of models and analytical results

The most important models and results of the manufacturing flow line literature are described. These include the major classes of models (asynchronous, synchronous, and continuous); the major features (blocking, processing times, failures and repairs); the major properties (conservation of flow, flow rate-idle time, reversibility, and others); and the relationships among different models. Exact and approximate methods for obtaining quantitative measures of performance are also reviewed. The exact methods are appropriate for small systems. The approximate methods, which are the only means available for large systems, are generally based on decomposition, and make use of the exact methods for small systems. Extensions are briefly discussed. Directions for future research are suggested.National Science Foundation (U.S.) (Grant DDM-8914277

Predico: A System for What-if Analysis in Complex Data Center Applications

Part 3: Storage and Performance ManagementInternational audienceModern data center applications are complex distributed systems with tens or hundreds of interacting software components. An important management task in data centers is to predict the impact of a certain workload or reconfiguration change on the performance of the application. Such predictions require the design of “what-if” models of the application that take as input hypothetical changes in the application’s workload or environment and estimate its impact on performance.We present Predico, a workload-based what-if analysis system that uses commonly available monitoring information in large scale systems to enable the administrators to ask a variety of workload-based “what-if” queries about the system. Predico uses a network of queues to analytically model the behavior of large distributed applications. It automatically generates node-level queueing models and then uses model composition to build system-wide models. Predico employs a simple what-if query language and an intelligent query execution algorithm that employs on-the-fly model construction and a change propagation algorithm to efficiently answer queries on large scale systems. We have built a prototype of Predico and have used traces from two large production applications from a financial institution as well as real-world synthetic applications to evaluate its what-if modeling framework. Our experimental evaluation validates the accuracy of Predico’s node-level resource usage, latency and workload-models and then shows how Predico enables what-if analysis in two different applications

Saving lives The NHS accident and emergency service and how to improve it

5.95SIGLEGBUnited Kingdo

The qnetworks Toolbox: a Software Package for Queueing Networks Analysis

Abstract. Queueing Networks (QNs) are a useful performance modelling notation. They can be used to describe many kinds of systems, and efficient solution techniques have been developed for some classes of QN models. Despite the fact that QNs have been extensively studied, very few software packages for QN analysis are available today. In this paper we describe the qnetworks toolbox, a free software package for QN analysis for GNU Octave. qnetworks provides implementations of solution algorithms for single station queueing systems as well as for product and some non product form QN models. Exact, approximate and bound analysis can be performed. Additional utility functions and algorithms for Markov Chains analysis are also included. The qnetworks package is available as free and open source software, allowing users to study, modify and extend the code. This makes qnetworks a viable teaching tool.