Browsing by Author "Deng, Yuhui"

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    Exploiting the performance gains of modern disk drives by enhancing data locality.
    (Elsevier, 2009-06-27) Deng, Yuhui
    Due to the widening performance gap between RAM and disk drives, a large number of I/O optimization methods have been proposed and designed to alleviate the impact of this gap. One of the most effective approaches of improving disk access performance is enhancing data locality. This is because the method could increase the hit ratio of disk cache and reduce the seek time and rotational latency. Disk drives have experienced dramatic development since the first disk drive was announced in 1956. This paper investigates some important characteristics of modern disk drives. Based on the characteristics and the observation that data access on disk drives is highly skewed, the frequently accessed data blocks and the correlated data blocks are clustered into objects and moved to the outer zones of a modern disk drive. The idea attempts to enhance spatial locality, improve the efficiency of aggressive sequential prefetch, and take advantage of Zoned Bit Recording (ZBR). An experimental simulation is employed to investigate the performance gains generated by the enhanced data locality. The performance gains are analyzed by breaking down the disk access time into seek time, rotational latency, data transfer time, and hit ratio of the disk cache. Experimental results provide useful insights into the performance behaviours of a modern disk drive with enhanced data locality.
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    LAG: Achieving transparent access to legacy data by leveraging grid environment
    (Elsevier Science B.V., Amsterdam., 2011-01-31T00:00:00Z) Deng, Yuhui; Wang, Frank Zhigang
    The world today is experiencing an explosive growth of data generated by information digitization. Due to the unprecedented advance in software and hardware, large amounts of data gradually becomes legacy data and inaccessible. This is building a digital black hole, and it is becoming a big challenge to access, process, and preserve the legacy data. Grid provides flexible, secure, and coordinated resource sharing among dynamic collections of individuals, institutions, and resources. It allows users and applications to access the aggregated resources in a transparent manner. This paper proposes a Legacy Application Grid (LAG) architecture. This architecture deploys diverse legacy applications in a grid environment and provides a transparent access to the remote LAG users who want to access the legacy data. In contrast to the existing methods which attempt to tackle legacy data and legacy applications, we wrap a display protocol into grid services. The service provider, who wants to deploy any legacy applications, just needs to deploy the protocol based grid service, describe and pass the parameters of those legacy applications to the service. Compared with the traditional approaches, the method proposed in this paper is very cost-effective because it avoids converting legacy data from one format to another format or upgrading legacy applications one by one. An implemented prototype validates that the LAG architecture trades acceptable performance degradation for a transparent and remote access to legacy data. (C) 2010 Elsevier B.V. All rights reserved.