Complete and fragmented replica selection and retrieval in Data Grids
Complete and fragmented replica selection and retrieval in Data Grids
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DOI：
10.1016/j.future.2006.09.006
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发表时间：
2007-05
期刊：
影响因子：
--
通讯作者：
R. Chang;Po-Hung Chen
中科院分区：
文献类型：
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作者：
R. Chang;Po-Hung Chen
数据网格支持广域网格系统中的数据密集型应用。他们通过复制数据集利用本地存储系统作为分布式数据存储。复制是分布式环境中常用的技术。复制的动机是复制可以提高数据可用性、数据访问性能和负载平衡。通常，一个完整的文件会被复制到许多网格站点以供本地访问。但是，站点可能只需要副本的一部分。因此，为了有效地使用存储系统，网格站点有必要仅存储副本的一部分。在本文中，我们提出了一个称为碎片副本的概念。也就是说，站点在进行复制时，只能存储本地需要的部分内容。可以大大节省因存储未使用的数据而浪费的存储空间。我们还提出了一个块映射过程来确定每个可用服务器中块的分布，以便以后进行副本检索。根据此过程，服务器可以提供其可用的部分副本内容以供网格系统中的其他成员访问。另一方面，客户端可以通过使用块映射过程直接检索碎片副本。在块映射过程之后，可以使用一些共同分配方案来从可用服务器检索数据集。模拟表明，共同分配方案还可以提高碎片复制系统中的下载性能。
Data Grids support data-intensive applications in wide area Grid systems. They utilize local storage systems as distributed data stores by replicating datasets. Replication is a commonly used technique in a distributed environment. The motivation of replication is that replication can improve data availability, data access performance, and load balancing. Usually a complete file is copied to many Grid sites for local access. However, a site may only need parts of a replica. Therefore, to use the storage systems efficiently, it is necessary for a Grid site to store only parts of a replica. In this paper, we propose a concept called fragmented replicas. That is, when doing replication, a site can store only some partial contents needed locally. It can greatly save the storage space wasted in storing unused data. We also propose a block mapping procedure to determine the distribution of blocks in every available server for later replica retrieval. According to this procedure, a server can provide its available partial replica contents for other members in the Grid system to access. On the other hand, a client can retrieve a fragmented replica directly by using the block mapping procedure. After the block mapping procedure, some co-allocation schemes can be used to retrieve data sets from the available servers. The simulation shows that the co-allocation schemes also improve download performance in a fragmented replication system.