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本文根据网格资源信息的特点阐述了由高度分布式的信息提供者和集合目录组成的网格信息服务基本框架。并分析了它的基础LDAP(Lightweight Directory Access Protocol)协议,指出LDAP目录本质是一种分布式的数据库。由于网格信息系统中LDAP目录信息树的动态刷新与复制的频繁发生,我们已提出用环形扩展和线形扩展策略来大幅度提高系统效率;在此基础上,本文进一步提出了文件分块复制法的思想把LDAP数据库文件分成若干块,在多个LDAP服务器端点间并行复制,最后实践证明,它大幅度提高了以LDAP目录分布式数据库为基础与核心的网格信息服务系统的并行效率。 相似文献
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针对分布式环境提出一种容错的文件数据复制与更新机制,其算法/协议建立在分布式算法理论的基础上,具有较强的容错性、故障恢复透明性和较高的效率,支持服务器同步和异步两种复制模式以及客户机启动与服务器启动两种工作方式。该机制可广泛应用于Internet分布式文件系统、分布式数据库、WEB镜像服务器以及分布式软件分发、群集服务器等应用中。 相似文献
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一种基于Grid的多媒体内容分布框架 总被引:1,自引:0,他引:1
基于互联网的大规模多媒体内容分发系统中,广泛地采用了数据复制技术来提高系统的性能。网格技术在构建大规模分布式信息系统方面,有着广阔的前景。本文提出了一种基于网格的多媒体内容分布框架,在网格基础服务的基础上,可以实现适用于流媒体应用的副本管理、传输和查找定位机制。此外,本文还对广域分布式信息系统中,副本的放置算法和用户请求调度机制等关键技术进行了深入探讨。 相似文献
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网格环境中基于对等代理的复制定位机制 总被引:1,自引:0,他引:1
针对目前网格环境中复制定位机制存在的问题,并综合考虑其中的优势,提出了一种基于对等代理的分布式复制定位机制,即通过对等代理组成分布式的虚拟全系统,实现全域网络里最大有效范围内的复制定位,比起传统的基于分级机制和分布式查询与索引机制的定位服务,在性能、安全、可靠性和有效性上都有很大的改善和提高。 相似文献
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针对分布式数据库中数据的分布性、事务执行的分布性和一些不可预测的软件错误和硬件故障等原因导致的数据不一致性问题,指出解决这些问题尚存在的困难,分析了消息队列法、事务控制法、复制控制法等分布式数据库中维护数据一致性的三种主要方法的缺点。在全局目录和分布式两阶段提交协议的基础上,提出了基于全局目录的分布式数据库数据一致性控制算法。该算法增强了分布式数据库中数据的一致性,节省了网络带宽,也提高了事务处理能力。 相似文献
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任何管理分布式网络的管理员都知道在网络中分发数据并保证数据的同步是多么痛苦的事。过去,数据分发并不是Windows系统的优势:大多数管理员使用旧的Robocopy工具来执行复制和同步工作,因为自带的文件复制服务(File Replication Service,FRS)并不能满足需求。 相似文献
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Chienwen WuGeneva G. Befford 《Computers & Industrial Engineering》1996,31(3-4):901-905
This paper presents a novel scheme for implementing the flexible replica control protocol[13] in the distributed database systems. The scheme requires less nodes to be locked to perform the read(write) operations. This not only provides better performance, but also provides the system designer extra flexibility to implement the protocol. 相似文献
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为了提高云存储系统的可扩展性、可靠性,同时改善用户访问能力,通常为其配备多数据副本机制,则不仅需要为数据副本选择合适的存储场地,而且需要实现用户访问请求对数据副本的优化分配。为此,提出了一种基于蚊子产卵交配和模拟退火混合优化数据副本放置机制。该机制以最小化总代价为优化目标,基于蚊子产卵交配思想确定数据副本候选放置方案,基于模拟退火进一步求精得到最优解。基于CloudSim,对该机制进行了仿真实现和性能评价,并且与现有的机制进行了对比分析,结果表明,该机制具有更好的性能,是可行和有效的。 相似文献
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Data replication techniques are used in data grid to reduce makespan, storage consumption, access latency and network bandwidth. Data replication enhances data availability and thereby increases the system reliability. There are two steps involved in data replication, namely, replica placement and replica selection. Replica placement involves identifying the best possible node to duplicate data based on network latency and user request. Replica selection involves selecting the best replica location to access the data for job execution in the data grid. Various replica placement and selection algorithms are available in the literature. These algorithms measure and analyze different parameters such as bandwidth consumption, access cost, scalability, execution time, storage consumption and makespan. In this paper, various replica placement and selection strategies along with their merits and demerits are discussed. This paper also analyses the performance of various strategies with respect to the parameters mentioned above. In particular, this paper focuses on the dynamic replica placement and selection strategies in the data grid environment. 相似文献
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In this paper, we study the quality-of-service (QoS)-aware replica placement problem in grid environments. Although there
has been much work on the replica placement problem in parallel and distributed systems, most of them concern average system
performance and have not addressed the important issue of quality of service requirement. In the very few existing work that
takes QoS into consideration, a simplified replication model is assumed; therefore, their solution may not be applicable to
real systems. In this paper, we propose a more realistic model for replica placement, which consider storage cost, update
cost, and access cost of data replication, and also assumes that the capacity of each replica server is bounded.
The QoS-aware replica placement is NP-complete even in the simple model. We propose two heuristic algorithms, called greedy remove and greedy add to approximate the optimal solution. Our extensive experiment results demonstrate that both greedy remove and greedy add find a near-optimal solution effectively and efficiently. Our algorithms can also adapt to various parallel and distributed
environments. 相似文献
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P. Victer PaulAuthor Vitae N. SaravananAuthor Vitae 《Future Generation Computer Systems》2012,28(3):573-582
Replica Management is a key issue to reduce the bandwidth consumption, to improve data availability and to maintain data consistency in large distributed systems. Global Replica Management (GRM) means to maintain the data consistency across the entire network. It is preferable particularly for multi-group distributed systems. On the other hand, GRM is not favorable for many applications because a very large number of message passes is needed for replica management processes. In this paper, in order to reduce the number of message passes needed to achieve the efficient GRM strategy, an interconnection structure called the Distributed Spanning Tree (DST) has been employed. The application of DST converts the peer network into logical layered structures and thereby provides a hierarchical mechanism for replication management. It is proved that this hierarchical approach improves the data availability and consistency across the entire network. In addition to these, it is also proved that the proposed approach reduces the data latency and the required number of message passes for any specific application in the network. 相似文献
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副本管理成为影响数据网格性能的主要因素之一,研究高效的副本管理算法大都依赖于对数据网格副本管理进行仿真.介绍了一种数据网格副本管理仿真软件的设计与实现,并详细介绍了数据网格仿真的一些关键技术的解决方案,如任务调度、任务执行仿真. 相似文献