Stochastic Workflow Scheduling with QoS Guarantees in Grid Computing Environments

Grid computing infrastructures embody a cost-effective computing paradigm that virtualises heterogenous system resources to meet the dynamic needs of critical business and scientific applications. These applications range from batch processes and long-running tasks to more real-time and even transactional applications. Grid schedulers aim to make efficient use of Grid resources in a cost-effective way, while satisfying the Quality-of-Service requirements of the applications. Scheduling in such a large-scale, dynamic and distributed environment is a complex undertaking. In this paper, we propose an approach to Grid scheduling which abstracts over the details of individual applications and aims to provide a globally optimal schedule, while having the ability to dynamically adjust to varying workloa

Resource allocation policies for service provisioning systems

This thesis is concerned with maximising the efficiency of hosting of service provisioning systems consisting of clusters or networks of servers. The tools employed are those of probabilistic modelling, optimization and simulation. First, a system where the servers in a cluster may be switched dynamically and preemptively from one kind of work to another is examined. The demand consists of two job types joining separate queues, with different arrival and service characteristics, and also different relative importance represented by appropriate holding costs. The switching of a server from queue i to queue j incurs a cost which may be monetary or may involve a period of unavail- ability. The optimal switching policy is obtained numerically by solving a dynamic programming equation. Two heuristic policies - one static and one are evaluated by simulation and are compared to the optimal dynamic - policy. The dynamic heuristic is shown to perform well over a range of pa- rameters, including changes in demand. The model, analysis and evaluation are then generalized to an arbitrary number, M, of job types. Next, the problem of how best to structure and control a distributed com- puter system containing many processors is considered. The performance trade-offs associated with different tree structures are evaluated approximately by applying appropriate queueing models. It is shown that. for a given set of parameters and job distribution policy, there is an optimal tree structure that minimizes the overall average response time. This is obtained numerically through comparison of average response times. A simple heuris- tic policy is shown to perform well under certain conditions. The last model addresses the trade-offs between reliability and perfor- mance. A number of servers, each of which goes through alternating periods of being operative and inoperative, offer services to an incoming stream of demands. The objective is to evaluate and optimize performance and cost metrics. A large real-life data set containing information about server break- downs is analyzed first. The results indicate that the durations of the oper- ative periods are not distributed exponentially. However, hyperexponential distributions are found to be a good fit for the observed data. A model based on these distributions is then formulated, and is solved exactly using the method of spectral expansion. A simple approximation which is accu- rate for heavily loaded systems is also proposed. The results of a number of numerical experiments are reported.EThOS - Electronic Theses Online ServiceBritish Telecom, North-East Regional e-Science CentreGBUnited Kingdo

Capacity planning and stochastic scheduling in grid computing environments

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Dynamic wavelength allocation in IP/WDM metro access networks

Ankara : The Department of Electrical and Electronics Engineering and the Institute of Engineering and Science of Bilkent University, 2008.Thesis (Ph.D.) -- Bilkent University, 2008.Includes bibliographical references leaves 132-139.Increasing demand for bandwidth and proliferation of packet based traffic have been causing architectural changes in the communications infrastructure. In this evolution, metro networks face both the capacity and dynamic adaptability constraints. The increase in the access and backbone speeds result in high bandwidth requirements, whereas the popularity of wireless access and limited number of customers in metro area necessitates traffic adaptability. Traditional architecture which has been optimized for carrying circuit-switched connections, is far from meeting these requirements. Recently, several architectures have been proposed for future metro access networks. Nearly all of these solutions support dynamic allocation of bandwidth to follow fluctuations in the traffic demand. However, reconfiguration policies that can be used in this process have not been fully explored yet. In this thesis, dynamic wavelength allocation (DWA) policies for IP/WDM metro access networks with reconfiguration delays are considered. Reconfiguration actions incur a cost since a portion of the capacity becomes idle in the reconfiguration period due to the signalling latencies and tuning times of optical transceivers. Exact formulation of the DWA problem is developed as a Markov Decision Process (MDP) and a new cost function is proposed to attain both throughput efficiency and fairness. For larger problems, a heuristic approach based on first passage probabilities is developed. The performance of the method is evaluated under both stationary and non-stationary traffic conditions. The effects of relevant network and traffic parameters, such as delay and flow size are also discussed. Finally, performance bounds for the DWA methods are derived.Yetginer, EmrePh.D

Dynamic Allocation of Servers in a Grid Hosting Environment

A grid hosting environment is described, where servers may be reconfigured dynamically from one type of work to another in response to changes in demand. The problem of carrying out these reconfigurations in the most efficient manner is addressed by means of stochastic modelling and optimization. A heuristic policy which is close to optimal over a wide range of parameters is introduced. A prototype system based on existing resource management software has been developed to demonstrate the concepts described

Dynamic Allocation of Servers in a Grid Hosting Environment

Abstract — A grid hosting environment is described, where servers may be reconfigured dynamically from one type of work to another in response to changes in demand. The problem of carrying out these reconfigurations in the most efficient manner is addressed by means of stochastic modelling and optimization. A heuristic policy which is close to optimal over a wide range of parameters is introduced. A prototype system based on existing resource management software has been developed to demonstrate the concepts described. Index Terms — Reconfigurable servers, Optimal resource allocation