We consider the resource allocation problem in distributed computing systems that have strict mutual consistency requirements. Our model incorporates the behavior of consistency control algorithms, which ensure that mutual consistency of replicated data is preserved even when communication links of the computer network and/or computers on which the files reside fail. The problem of resource allocation in these networks is significant in terms of the efficiency of operations and the reliability of the network. The constrained resource allocation problem is formulated as a mixed nonlinear integer program. An efficient algorithm is proposed to solve this problem. The performance of the algorithm is evaluated in terms of the algorithm's accuracy, efficiency and execution times, using a representative problem set. 1 Introduction Consider a distributed computing system (DCS) that is made up of a set of sites (nodes) connected through communication links which transmit information from one s...

Abstract: Storing multiple copies of files is crucial for ensuring quality of service for data storage in mobile networks. This paper proposes a new scheme, called the K-out-of-N file distribution scheme, for the placement of files. In this scheme files are splitted, and Reed-Solomon codes or other maximum distance seperable (MDS) codes are used to produce file segments containing parity information. Multiple copies of the file segments are stored on gateways in the network in such a way that every gateway can retrieve enough file segments from itself and its neighbors within a certain amount of hops for reconstructing the orginal files. The goal is to minimize the maximum number of hops it takes for any gateway to get enough file segments for the file reconstruction. We formulate the K-out-of-N file distribution scheme as a coloring problem we call diversity coloring. A diversity coloring is defined to be optimal if it uses the smallest number of colors. Upper and lower bounds on the performance of diversity coloring for general graphs are studied. Diversity coloring algorithms for several special classes of graphs—trees, rings and tori—are presented, all of which have linear time complexity. Both the algorithm for trees and the algorithm for rings output optimal diversity colorings. The algorithm for tori guarantees to output optimal diversity coloring when the sizes of tori are sufficiently large. Index Terms: Data storage, diversity coloring, file assignment problem (FAP), graph coloring, K-out-of-N scheme, maximum distance seperable (MDS) codes, mobile computing, Quality of Service

Q uantitative M odeling I n P arallel S ystems

Suppose you got an excellent dynamic file assignment algorithm. But, how to proceed dynamically from the current to the optimal file allocation? Imagine replication of your files and some sort of voting strategy --- the question then is, how to maintain consistency if the current and the optimal file assignment differ not only in the location of the files but also in the number of replicas? This paper tries to answer these questions and introduces the basic relocation protocols which preserve consistency during relocation, as well as a priority-driven, storage capacity-based approach to bring the basic relocation protocols in an optimal sequence in order to move quickly and as close as possible towards the optimal file assignment. 1 Introduction We consider a mathematical model of an information network of jRj nodes, some of which contain copies of our jDj data files. The degree of replicas has not to be fixed. Within this network, every node is able to communicate with every other no...

. In the design of distributed systems, the strategy used for process allocation has a great impact on the system performances. Most of the proposed dynamic allocation algorithms are based on heuristics, because of the impossibility to have a coherent global state of a distributed system and the time constraints of the process allocation decision making. In this report, a review and a comparative study of the different research studies in this field are presented. We propose a classification of the dynamic allocation algorithms, following the strategy used in the information exchange protocol to maintain the current state of a distributed system, and the process placement protocol to localize the destination of a process. The use of process migration mecanism is also analysed. Mots cl' es : Allocation dynamique de processus, Distribution de la charge, Localit'e, Migration de processus. Keywords : Dynamic process allocation, Load balancing, Locality, Process migration. 1 Introduction ...

There is now considerable interest in industry and academia for “autonomic” or self-adaptive networks and distributed systems. Large-scale applications, such as simulation, typically run on large distributed systems in which it is impossible to guarantee at each instant the full reliability and availability of all processing nodes and of all communication links. Nevertheless such systems have to accomplish their mission and provide a high level of dependability and the best possible performance to critical applications. Self-adaptation will therefore be an intrinsic feature of large distributed systems and networks in order to move tasks and files in response to changes in subsystem dependability and system load, and to provide Quality-of-Service and dependable connections in the presence of fluctuating workloads and unknown system behavior. In this paper we review our work on the design of adaptive on-line task management algorithms for distributed systems, and the control of cognitive packet networks (CPN) to offer user specified QoS.