Several co-allocation strategies have been coupled and used to exploit rate differences among various client-server links and to address dynamic rate fluctuations by dividing files into multiple blocks of equal sizes. However, a major obstacle, the idle time of faster servers having to wait for the slowest server to deliver the final block, makes it important to reduce differences in finishing time among replica servers. In this paper, we propose a dynamic co-allocation scheme, namely RecursiveAdjustment Co-Allocation scheme, to improve the performance of data transfer in Data Grids. Our approach reduces the idle time spent waiting for the slowest server and decreases data transfer completion time.

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SUMMARYData Grids enable the sharing, selection, and connection of a wide variety of geographically distributed computational and storage resources for addressing large-scale data-intensive scientific application needs in, for instance, high-energy physics, bioinformatics, and virtual astrophysical observatories. Data sets are replicated in Data Grids and distributed among multiple sites. Unfortunately, data sets of interest sometimes are significantly large in size, and may cause access efficiency overhead. A co-allocation architecture was developed in order to enable parallel downloading of data sets from multiple servers. Several co-allocation strategies have been coupled and used to exploit download rate by specifying among various client-server divides files into multiple blocks of equal sizes to link and address dynamic rate fluctuations. However, one major obstacle, the idle time of faster servers having to wait for the slowest server to deliver the final block, makes it important to reduce differences in finishing time among replica servers. In this paper, we propose a dynamic co-allocation method, called Recursively Adjusting Co-Allocation Method (RACAM), to improve the performance of parallel data file transfer. Our approach reduces the idle time spent waiting for the slowest server and decreases data transfer completion time. We also provide an effective scheme for reducing the cost of reassembling data blocks.