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Abstract: Server performance is one of the critical activities in the data grid environment. A large number of applications require access to huge volumes of data from grid servers. In this case, efficient, scalable and robust grid server which can deal with large file transfer concurrent is needed. In this paper, we analyze the bottleneck of our grid servers and introduce user-space I/O scheduling, zero copy and event-driven architecture in our grid server to improve the servers’ performance. The user-space I/O scheduling can save almost 50% I/O time in a huge number of small files transfer. Grid servers can elimination CPU consumptions between kernel and user space by zero copy and cut 63% times for context switches. Event-driven architecture will save 30% CPU usage to reach the best performance by thread-driven architecture. Optimization method combination of these three above are used in our grid servers, the full-load throughput of our system is 30% more than traditional solutions and only 60% CPU consumed compared with traditional solutions. [Copyright &y& Elsevier]

Abstract: We study the broadcast scheduling problem in which clients send their requests to a server in order to receive some files available on the server. The server may be scheduled in a way that several requests are satisfied in one broadcast. When files are transmitted over computer networks, broadcasting the files by fragmenting them provides flexibility in broadcast scheduling that allows the optimization of per user response time. The broadcast scheduling algorithm, then, is in charge of determining the number of segments of each file and their order of transmission in each round of transmission. In this paper, we obtain a closed form approximation formula which approximates the optimal number of segments for each file, aiming at minimizing the total response time of requests. The obtained formula is a function of different parameters including those of underlying network as well as those of requests arrived at the server. Based on the obtained approximation formula we propose an algorithm for file broadcast scheduling which leads to total response time which closely conforms to the optimum one. We use extensive simulation and numerical study in order to evaluate the proposed algorithm which reveals high accuracy of obtained analytical approximation. We also investigate the impact of various headers that different network protocols add to each file segment. Our segmentation approach is examined for scenarios with different file sizes at the range of 100 KB to 1 GB. Our results show that for this range of file sizes the segmentation approach shows on average 13% tolerance from that of optimum in terms of total response time and the accuracy of the proposed approach is growing by increasing file size. Besides, using proposed segmentation in this work leads to a high Goodput of the scheduling algorithm. [Copyright &y& Elsevier]

This paper outlines the way the planning/scheduling applications can be solved using the optimization potential of the Choco CSP solver. Consequently two specific problems which can be applied in various fields were described in this paper. The first one is a pure planning problem and supposes that a factory should manufacture products ordered by a client in the shortest time possible. The second one is a scheduling problem regarding simultaneous file transmission-visualization, where the task is to determine the start moments of the copy operations. The results show that both problems, otherwise difficult to solve in a classical way, can be solved readily using the CSP approach. [ABSTRACT FROM AUTHOR]