共查询到19条相似文献,搜索用时 296 毫秒
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对于具有海量信息的数字图书馆,文章针对不同请求服务时间变化大的特性,提出基于请求类型的负载平衡模型,该模型根据各种不同请求对服务器负载状况的影响并结合各服务器的性能进行动态负载调度。避免占用服务器资源较多的请求同时分配到同一台服务器上。仿真结果表明该模型具有良好的负载平衡效果。有效地缩短了用户请求的响应时间。 相似文献
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服务器集群可显著提高整个分布式系统的总体性能。本文针对用户请求服务时间变化大的特性,设计了一个跨平台、跨系统的动态负载均衡中间件工作模型,并对其中的关键问题给予详细描述。模型根据各服务器动态返回的负载信息并结合各服务器的性能进行动态负载调度,并以标准服务接口实现与分布式系统的无缝集成。性能测试表明该模型有效解决了集群的负载均衡问题。 相似文献
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文中提出了一种新颖的异构服务器负载均衡方法,在传统的均衡系统吞吐量的基础上,考虑到各服务器的处理能力,通过加入服务器处理能力权重和概率选择向量,对每一个到来的请求计算其概率向量进行任务分配。这种方法从理论上分析应能解决系统调度方面资源的耗费最小的问题,对不同性能的服务器最大可能的保持负载平衡,并且使客户请求在最短时间内得到回复。而实验也表明,该方法是有效的。 相似文献
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《计算机应用与软件》2013,(8)
针对现有服务器集群的负载平衡算法不足,提出一种应用层自适应动态负载平衡算法。利用应用层特点,在负载均衡服务器端收集应用服务器负载信息,提出一种综合的权重计算方法,动态区分不同状态的服务器。通过自适应选择算法,合理分配请求至应用服务器。实验结果表明,在不同的负载情况下,该算法能有效地平衡负载,充分利用服务器资源。 相似文献
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文中提出了一种二叉树动态负载平衡方法,该方法使用二叉树动态负载平衡系统模型,解决了集中式负载平衡系统中主结点在分配任务、响应请求以及负载移动时的潜在瓶颈问题;提出了负载小于给定值时请求负载平衡以提高处理器的利用率。分析表明,该方法在可以有效地提高并行计算的性能,特别是对于任务密集的情况。 相似文献
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集群系统中自适应负载反馈平衡策略的研究 总被引:2,自引:0,他引:2
当前在集群系统中,负载平衡策略虽然很多,但是为了减少反馈开销,一般策略为采用在前端估计后端负载,所以不能很好地完成负载平衡的任务。针对这一问题,提出了一种自适应负载反馈平衡策略,各个服务器根据自身负载的变化来决定负载反馈的时机,前端根据负载信息和请求率计算出各个服务器的负载权值,最后根据负载权值来调度服务器处理请求,以实现负载平衡。由于采用了自适应的反馈策略,在获得各个服务器负载信息的同时减少了负载反馈的开销,实现了系统的负载均衡。测试结果表明该策略表现出了一定的优势。 相似文献
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为了解决目前Web服务集群存在的问题,提出了一个双层分配器负载平衡模型。在确定了负载指标的基础上,给出了该模型的负载平衡算法。并就服务器迅速过载问题和容错性问题提出了初步的解决方案。最后,对模型的性能进行了测试,结果表明模型达到了较好的负载平衡。 相似文献
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针对现有多目标调度方法所需时间较长以及处理突发情况时性能降低的问题,提出一种基于模因优化和循环调度的多目标负载均衡技术。使用突发检测器检测发送到云服务器的用户请求,确定负载状态。基于测器结果,应用不同的负载平衡算法来高效地调度用户任务。利用选定的负载平衡算法将用户请求任务调度到资源最佳的虚拟机上,保证在最低的时间消耗内达到负载均衡的状态。实验结果表明,与其他算法相比,该方法在多个性能指标上具有明显优势,可以提高调度效率的同时,最大限度地降低云中的能源使用。 相似文献
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在对服务器集群Web QoS控制基础上,综合考虑请求内容和各服务器性能以及当前整个集群负载平衡状况,设计了一种基于L4/L7双层分配的混合负载平衡调度策略,算法引入了一个反馈环节动态地改变Web服务器的权值,通过负载平衡程度的阈值进行判断,选择不同的调度策略,从而提高了Web集群系统的性能。 相似文献
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一种基于网络地址转换的负载均衡算法 总被引:1,自引:4,他引:1
本文探讨集群服务器使用的负载均衡技术及负载分配的策略,并将网络地址转换应用于VOD集群,将负载分给多个服务器分担,以解决VOD集群服务器面临的大量并发访问造成的CPU或I/O的高负载问题。为了达到最佳的负载均衡效果,负载均衡器需要根据各个服务器的当前CPU和I/O状态来分配负载,这就需要动态监视服务器的负载,并应用优化的负载分配策略,达到平均分配负载的目的。 相似文献
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In a large-scale multimedia storage system (LMSS) where client requests for different multimedia objects may have different demands, the placement and replication of the objects is an important factor, as it may result in an imbalance in server loading across the system. Since replication management and load balancing are all the more crucial issues in multimedia systems, in the literature, these problems are handled by centralized servers. Each object storage server (OSS) responds to the requests that come from the centralized servers independently and has no communication with other OSSs in the system. In this paper, we design a novel distributed load balancing strategy for LMSS, in which OSSs can cooperate to achieve higher performance. Such OSS modeled as an M/G/m system can replicate the objects to and balance the requests among other servers to achieve a near-optimal average waiting time (AWT) of the requests in the system. We validate the performance of the system via rigorous simulations with respect to several influencing factors and prove that our proposed strategy is scalable, flexible, and efficient for real-life applications. 相似文献
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随着过去几十年互联网服务的指数增长,各大网站的访问量急剧上升。海量的用户请求使得热门网站的网络请求率可能在几秒钟内大规模增加。一旦服务器承受不住这样的高并发请求,由此带来的网络拥塞和延迟会极大地影响用户体验。负载均衡是高可用网络基础架构的关键组件,通过在后端引入一个负载均衡器,将工作负载分布到多个服务器来缓解海量并发请求对服务器造成的巨大压力,提高后端服务器和数据库的性能以及可靠性。而Nginx作为一款高性能的HTTP和反向代理服务器,正越来越多地应用到实践中。文中将分析Nginx服务器负载均衡的体系架构,研究默认的加权轮询算法,并提出一种改进后的动态负载均衡算法,实时收集负载信息,重新计算并分配权值。通过实验测试,对比不同算法下的负载均衡性能,改进后的算法能有效提高服务器集群的性能。 相似文献
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Service providers have begun to offer multimedia-on-demand services to residential estates by installing isolated, small-scale multimedia servers at individual estates. Such an arrangement allows the service providers to operate without relying on a highspeed, large-capacity metropolitan area network, which is still not available in many countries. Unfortunately, installing isolated servers can incur very high server costs, as each server requires spare bandwidth to cope with fluctuations in user demand. The authors explore the feasibility of linking up several small multimedia servers to a (limited-capacity) network, and allowing servers with idle retrieval bandwidth to help out servers that are temporarily overloaded; the goal is to minimize the waiting time for service to begin. We identify four characteristics of load sharing in a distributed multimedia system that differentiate it from load balancing in a conventional distributed system. We then introduce a GWQ load sharing algorithm that fits and exploits these characteristics; it puts all servers' pending requests in a global queue, from which a server with idle capacity obtains additional jobs. The performance of the algorithm is captured by an analytical model, which we validate through simulations. Both the analytical and simulation models show that the algorithm vastly reduces wait times at the servers. The analytical model also provides guidelines for capacity planning. Finally, we propose an enhanced GWQ+L algorithm that allows a server to reclaim active local requests that are being serviced remotely. Simulation experiments indicate that the scheduling decisions of GWQ+L are optimal, i.e., it enables the distributed servers to approximate the performance of a large centralized server 相似文献
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Web应用服务器是Web计算环境下产生的新型中间件,为创建、部署、运行、集成和管理事务性Web应用提供一个跨平台的运行环境,被认为是自关系型数据库以来最令人激动的企业应用技术.诸多IT企业纷纷推出其各自的Web应用服务器产品和系统,学术界也对这种热门领域产生了浓厚的兴趣.在分析Web计算环境下传统中间件发展所遇到的问题的基础上,介绍Web应用服务器的起源和发展、运行模式以及评测基准,然后对Web应用服务器研究现状进行综述,主要包括Web应用服务器的定义、体系结构、组件容器、分布事务处理、负载平衡、高速缓存、Web Service等研究热点和关键技术.根据评测基准,对若干主流Web应用服务器从功能和性能两个方面进行分析和比较.此外,还指出了Web应用服务器目前存在的不足以及未来的发展趋势. 相似文献
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Saeed Sharifian Seyed A. Motamedi Mohammad K. Akbari 《The Journal of supercomputing》2010,53(3):440-463
The growth of web-based applications in business and e-commerce is building up demands for high performance web servers for
better throughputs and lower user-perceived latency. These demands are leading to a widespread substitution of powerful single
servers by robust newcomers, cluster web servers, in many enterprise companies. In this respect the load-balancing algorithms
play an important role in boosting the performance of cluster servers. The previous load-balancing algorithms which were designed
for the handling of static contents in web services suffer from significant performance degradation under dynamic and database-driven
workloads. Regarding this, we propose an approximation-based load-balancing algorithm with admission control for cluster-based
web servers in this study. Since it is difficult to accurately determine the loads of web servers through feedbacks from distributed
agents in web servers, we propose an analytical model of a web server to estimate the web servers’ loads. To achieve this,
the algorithm classifies requests based on their service times and track numbers of outstanding requests for each class of
each web server node and also based on their resource demands to dynamically estimate the loads of each node. For the error
handling of the model a proportional integral (PI) controller from control theory is used. Then the estimated available capacity
of each web server is used for load balancing and admission control decisions. The implementation results with a standard
benchmark confirm the effectiveness of the proposed scheme, which improves both the mean response time and the throughput
of the cluster compared to rival load-balancing algorithms, and also avoids situations in which the cluster is overloaded,
even when the request rates are beyond the cluster capacity. 相似文献