Hsi-Min Chen

Dynamic resource selection heuristics for a non-reserved bidding-based Grid environment

A Grid system is comprised of large sets of heterogeneous and geographically distributed resources that are aggregated as a virtual computing platform for executing large-scale scientific applications. As the number of resources in Grids increases rapidly, selecting appropriate resources for jobs has become a crucial issue. To avoid single point of failure and server overload problems, bidding provides an alternative means of resource selection in distributed systems. However, under the bidding model, the key challenge of resource selection is that there is no global information system to facilitate optimum decision-making; hence requesters can only obtain partial information revealed by resource providers. To address this problem, we propose a set of resource selection heuristics to minimize the turnaround time in a non-reserved bidding-based Grid environment, while considering the level of information about competing jobs revealed by providers. We also present the results of experiments conducted to evaluate the performance of the proposed heuristics.

Efficient multi-source data transfer in data grids

As the number of data-intensive applications increases in various domains, scientists need to save, retrieve, and analyze increasingly large datasets. The huge volume of data and the long latency of data transfer on the Internet make it very difficult to ensure high-performance access to data grids. Thus, data replication techniques have been widely adopted to solve the latency problem. In this paper, we propose an efficient data replication algorithm for multi-source data transfer, whereby a data replica can be assembled in parallel from multiple distributed data sources and adapted to the variability of network bandwidths. The experimental results show that the proposed algorithm can obtain more aggregated bandwidth, reduce connection overheads, and achieve superior load balance.

A dual-mode exerciser for a collaborative computing environment

Computer-supported cooperative work (CSCW) supports groups with communication and coordination during the execution of their activities. It allows physically dispersed teams to engage in a common task by providing an interface to a shared workspace. A variety of synchronous applications are playing a major role in distance education, joint program development, cooperative publishing, etc. These applications are usually platform-dependent, groupware programmers have to develop new applications for each groupware platform. In this paper, we present a developing environment called CollabRunJava. Users can collaborate to design and process their job and can also develop groupware only concentrate on application-specific details on our system. CollabRunJava supports 2 modes for developing applications. In the instant-develop mode, user can immediately execute and test the classes. In the runtime-evolution mode, user can observe application behavior, debug applications and change the running applications codes without re-execution. Our system can be further enhanced by using plug-in components with the above mechanisms. For example, with the aid of visualization components, our system can help users explore program behavior. In addition, all these activities can be performed in a collaborative way. This makes it also helpful for distant learning and program testing.

Middleware of Taiwan UniGrid

Taiwan UniGrid (Taiwan <u>Uni</u>versity <u>Grid</u>) is a Grid computing platform, which is founded by a community of educational and research organizations interested in Grid computing technologies in Taiwan. In this paper, we present the design and development of a middleware for Taiwan UniGrid. Taiwan UniGrid middleware consists of three primary modules: 1) UniGrid Portal, 2) Computing Service, and 3) Data Service. We explain the major design issues that we suffered from the development of these three modules and propose the corresponding approaches to them. The detailed system architecture, software components and features are elaborated. Finally, an example of a workflow consisting of MPI parallel jobs demonstrates that users can utilize Grid resources with ease via our middleware platform.

Optimizing server placement in hierarchical grid environments

Abstract In this paper, we address some problems related to server placement in Grid environments. Given a hierarchical network with requests from clients and constraints on server capability, the minimum server placement problem attempts to place the minimum number of servers that satisfy requests from clients. Instead of using a heuristic approach, we propose an optimal algorithm based on dynamic programming to solve the problem. We also consider the balanced server placement problem, which tries to place a given number of servers appropriately so that their workloads are as balanced as possible. We prove that an optimal server placement can be achieved by combining the above algorithm with a binary search on workloads. This approach can be further extended to deal with constrains on network capability. The simulation results clearly show the improvement in the number of servers and the maximum workload. Furthermore, as the maximum workload is reduced, the waiting time is reduced accordingly.

A Reliability-Aware Approach for Web Services Execution Planning

The dynamic composition of Web services from independent service providers for complicated distributed applications is emerging as a key technique in the Internet world for future critical software systems. In such an environment, a user may need to compose some Web services to perform critical tasks along a given execution path that needs high reliability to avoid unacceptable failures due to service crashes. To achieve high reliability, the active parallel replication and standby parallel replication strategies can be used for managing the redundancy existing in each task of an execution plan. However, more replicas of Web services used during a task execution means higher price a user has to pay for. In this paper, we propose an approach to select necessary Web services from different vendors for the purpose of their composition in a way that satisfies the user-specified reliability, price and response time, while trying to minimize the price and delay of an execution plan. We provide simulation results to study the performance of the proposed approach and compare it with four variations that use different heuristics for service selections.

Resource Selection Strategies for a CNP-Based Resource Management Model

In this paper, we propose a resource management model that extends the contract net protocol by integrating the advantages of the matchmaking technique. Our model addresses the issues of matchmaker overload and the lack of up-to-date resource state information suffered by the original matchmaking model. It also enables resource requesters to obtain a list of qualified resources with which they can narrow down the selection of resources and reduce the number of ineffective communication messages. In addition, we present five strategies to facilitate resource selection on our model from the perspective of turnaround time and reporton experiments to evaluate their performance. The experiment results show that, in the presence of resource contention, the probabilistic strategies outperform random and the deterministic ones, and the performance of the presented strategies executed on our model is superior to their performance on the original matchmaking model.

A high-performance virtual storage system for Taiwan UniGrid

In Taiwan, a community of educational and research organizations interested in Grid computing technologies founded a Grid computing platform, called Taiwan UniGrid. Taiwan UniGrid consists of three primary portions: Computational Grid, Data Grid, and Web Portal. In this paper, we present the development of a virtual data storage system for Taiwan UniGrid. In addition to developing basic data storage functions, we identify three main requirements of the current development: high-performance data transfer, data sharing and single sing-on. For these requirements, we come up with three corresponding features in our data storage system: Self-Adaptation for high-performance data transfer, forming user groups and specifying admission control for data sharing, and adopting GSI authentication to enable single sing-on. Besides, we also develop a Java-based graphic user interface of the storage system that allows Grid users to manage data transparently as using local file systems.

Conformance Checking of Running Programs in Dynamic Aspect-Oriented Systems

A dynamic aspect-oriented system weaves aspects into applications at run time. As a result, a static model can be dynamically modified to include the codes needed to fulfill non-functional requirements without having to shut down the running program. Although this provides a high degree of flexibility, it may lead to a conformance problem. In this paper, we study the conformance issues of aspect-oriented programs and propose a scheme to check the conformance of running programs with the original software specification in dynamic aspect-oriented systems. First, we propose extensions of the UML model to express the specification of aspect-oriented applications, after which we study and classify typical mistakes made in deploying aspects. Then, we design a scheme to check if the current state conforms to the software specification. We take JAsCo as the target system to implement the proposed scheme. When the program starts running or aspects in the registry are changed, the system informs the developers if the current state violates the software specification.

Towards a service-based collaborative framework for data-intensive grid applications

As data-intensive applications increase continuously in various domains, scientists nowadays need to save, retrieve and analyze rapidly increasing large datasets. The long latency of data transfer over Internet results in a serious challenge on ensuring high-performance access to large quantities of data. Furthermore, the vision of grid researches is to provide a collaborative space where scientists can share their data, resources and experiences with others. These issues motivate us to develop a service-based collaborative framework for data-intensive grid applications. In this paper, we describe our initial work towards this goal. We plan to provide an integrated and virtual infrastructure, which manages distributed and diverse data resources and services. By means of Web Services technologies, we can realize the interoperability among various types of resources and integrate computing services with storage services to serve data-intensive applications. By making use of portals and data-intensive applications built on the top of the framework, users will be able to manage and analyze large quantities of data with high performance and share useful data with others in a way of forming virtual groups to complete cooperative work.