高可用双机容错服务器的研究与设计

为了保证服务器对外服务的持续性,提高服务器的可靠性,双机容错服务器是一种较好的解决方案.通过引入集群技术设计了高可用双机容错服务器的硬件容错体系,使用自检和心跳等多种软件容错技术实现了运行于该容错服务器之上的容错管理系统,最后对该容错系统给出了可用性分析.     

基于SCO Unix双机容错热备份技术的实现

基于SCO Unix平台的双机容错热备份系统技术在铁路、邮电、电力、金融等部门的网络系统中有广阔的应用前景,本文结合网络设计实践,提出了该系统的软硬件设计方案,及使用sentinel双机容错软件在SCOUnix平台上,成功实现了双机容错热备份技术.     

基于Oracle数据库的双机集群系统的设计与实现

通过简述集群技术的应用与双机容错技术的基本原理与优势,依据实例研究在在双机集群环境下实现Oracle并行服务的方法,实现了软、硬件上的容错以及动态负载均衡等高可用功能.     

论社区网格化管理平台的可靠性分析与设计

描述了平台概况,介绍了常用的冗余方法、软件容错技术、双机容错技术和集群技术等容错技术,并结合我区社区管理信息化创新平台建设,阐述了该平台采取的接入层虚拟化双机冗余、软件容错技术、数据库服务器双机容错技术与服务器虚拟化集群技术等多项容错技术.通过采用这些技术显著提高了该信息系统的可靠性,确保了社区管理与综合服务的质量.     

在双机集群环境下Oracle并行服务的实现分析

简要介绍了集群技术在当今的应用,双机容错技术的基本原理与实现和Oracleb并行服务的基本原理,通过应用实例探讨了在双机集群环境下实现oracle并行服务的方法,并对构建并行系统时所出现的一些问题,提出了尝试性的解决方案。     

实时双机嵌入式容错系统实现与可调度性研究

针对电力直流监控系统的可靠性要求,采用实时双机嵌入式容错系统的设计以实现功能.采用了基于内核抢占式的实时多任务操作系μC/OS-Ⅱ进行容错设计、修改了内核调度,并讨论、验证了容错的任务可调度性.可靠性检测结果表明,双机容错系统的功能可以满足实际要求.     

一种纯软件的双机热备份算法

随着对系统可靠性认识的不断深化，容错技术有了比较大的发展，出现了集群等容错方案，由于具体的系统可靠指标不同，针对一个实际的系统可靠性的指标，提出了一种纯软件双机热备份算法，该算法既简洁明了，容易实现，又满足了系统的可靠性指标。     

基于RAID的双机集群系统应用研究*

对集群相关技术进行分析,提出了基于RAID的双机集群系统的两种应用模式.该模式通过功能整合和故障过渡技术实现集群系统的高可用性和高可靠性.     

双机容错系统

双机双控容错系统方案是由二台服务器共同担任同一工作。当一台服务器出现故障时,另一台服务器仍然可确保系统正常运行,从而保障了系统的高可靠性、高安全性和高可用性,将系统风险降低到最低限度。双机双控系统的技术基础是近年来成熟起来的集群(Cluster)结构。Cluster集群技术的出发点是提供高可靠性、可扩充性和抗灾难性。一个Cluster包含多台拥有共享数据存储空间的服务器,各服务器通过内部局域网相互通信。当一台服务器发生故障时,它所运行的应用程序将由其他服务器自动接管。这里以HP公司的NetServer服务器为例,对双机双控容错系统作一简单的介绍。Hp NetServer针对Cluster技术做了许多优化和改进,提供了相     

数据库双机热备份系统解决方案

如何保证核心应用永不停止,关键数据不会丢失?越来越多的企业采用双机热备份或多机集群技术来解决这一问题.RAID是提高数据安全性和读写性能的一种廉价使用磁盘驱动器的方法,通过在两台服务器上运行双机热备份软件和共用RAID5磁盘阵列实现双机热备系统,相对于多机集群技术,其技术成熟,成本较低.     

一种用于可扩展计算集群作业分配的机会成本方法

计算集群的系统资源的使用对于系统的性能至关重要,而作业分配策略直接影响系统的计算能力。该文提出了一个用于计算集群中机器之间作业分配和重分配的“机会成本”方法。该方法将某台机器内各种异质资源的使用转变为某一同质的“成本”,而作业的分配与重分配则基于该成本。     

RKB／PL：C＋＋的持久性扩充

需求工程知识库／ＰＬ——ＲＫＢ／ＰＬ（ｒｅｑｕｉｒｅｍｅｎｔ—ｅｎｇｉｎｅｅｒｉｎｇｋｎｏｗｌｅｄｇｅｂａｓｅ／ＰＬ）是保持Ｃ＋＋原有风格对Ｃ＋＋进行的持久性扩充．为支持对象的持久性,ＲＫＢ／ＰＬ在Ｃ＋＋对象类的基础上扩充了以约束声明加强对象状态的用户监控;引入簇来表达对象类的集合含义;引入集合、簇、簇闭包的遍历机制来支持对象查询．为支持这些语言机制,ＲＫＢ／ＰＬ具有一个由一组ｂｕｉｌｄ—ｉｎ对象类层次、类型信息库及接口函数、系统状态表以及系统服务函数等构成的运行时系统．本文讨论了ＲＫＢ／ＰＬ中这些机制的表示、相应的运行时系统的组成以及它们的主要实现技术．ＲＫＢ／ＰＬ已成功地用于实现“软件需求获取助手ＦＲＡ”系统的需求工程知识库子系统．     

集群协作缓存机制研究

计算机集群中的节点使用内存一般不均衡,往往有些节点使用太多内存,而其他节点又有较多的空闲内存.为了改进集群操作系统,将集群节点的内存作全局分布的资源使用,我们首先提出一个内存互操作高速缓存方案:通过使用集群范围内的内存作文件高速缓存,从其他节点的高速缓存中读文件,可以避免很多低速的磁盘访问,改进集群文件系统的总体吞吐量.然后利用我们提出的缓存页面代替策略GCAR来支持这种内存互操作的高速缓存方案.该算法与CAR相比,对缓存中被"经常"使用的页面的管理粒度更细,更适合集群协作缓存的计算环境.实验结果表明,GCAR对本地缓存的命中率比CAR略好,在集群协作缓存下能取得更好的缓存命中率.     

A distributed implementation of a virtual machine for Java

The cluster virtual machine (VM) for Java provides a single system image of a traditional Java Virtual Machine (JVM) while executing in a distributed fashion on the nodes of a cluster. The cluster VM for Java virtualizes the cluster, supporting any pure Java application without requiring that application be tailored specifically for it. The aim of our cluster VM is to obtain improved scalability for a class of Java Server Applications by distributing the application's work among the cluster's computing resources. The implementation of the cluster VM for Java is based on a novel object model which distinguishes between an application's view of an object (e.g. every object is a unique data structure) and its implementation (e.g. objects may have consistent replications on different nodes). This enables us to exploit knowledge on the use of individual objects to improve performance (e.g. using object replications to increase locality of access to objects). We have already completed a prototype that runs pure Java applications on a cluster of NT workstations connected by a Myrinet fast switch. The prototype provides a single system image to applications, distributing the application's threads and objects over the cluster. We used the cluster VM to run, without change, a real Java Server Application containing over 10 Kloc

1 Kloc means Kilo lines of code—used to describe the size of applications in terms of source lines count.

for the source code and achieved high scalability for it on a cluster. We also achieved linear speedup for another application with a large number of independent threads. This paper discusses the architecture and implementation of the cluster VM. It focuses on achieving a single system image for a traditional JVM on a cluster while describing, in short, how we aim to obtain scalability. Copyright © 2001 John Wiley & Sons, Ltd.     

一种基于聚类的对等网络图像搜索机制

将基于内容的图像检索应用到P2P网络中,提出了一种基于“类簇”的P2P网络信息搜索机制。结合聚类方法和Small world原理,将相似的图像文件聚集到同一个“类簇”中,不同簇之间建立远距离连接;查询时先定位到所属的簇,在簇内广播查询,并根据查询记录更新节点路由表。仿真实验表明该搜索机制具有良好的搜索性能。     

基于奇偶轮成簇和双簇首的非均匀分簇协议

针对无线传感器网络（WSN）存在"能量热区"和系统鲁棒性较差的问题,提出了一种基于奇偶轮成簇和双簇首的非均匀分簇协议（UCOD）。首先,优化竞争半径函数,使簇首分布更合理;其次,引入主副簇首机制,当主簇头能量低于设定的能量阈值时进入休眠,副簇头同时执行主副簇头功能以提高鲁棒性;然后,采用奇偶轮不同的成簇机制,奇数轮全局节点竞争簇首,偶数轮在奇数轮簇内选择簇首,减少节点入簇选择耗能;最后,将网络分级,节点根据位置、能量、转发次数和周围节点数在下一级选择中继节点。仿真结果表明,UCOD与分布式能量均衡非均匀分簇协议（DEBUC）和基于非均匀分簇的无线传感器网络分层路由协议（HRPNC）相比,网络生命周期延长了28.4%和13.7%,丢包率在簇首损坏50%的情况下降低了39.1和27.5个百分点。实验结果表明,UCOD能够有效提高能量效率和系统鲁棒性。     

PowerDB-IR – Scalable Information Retrieval and Storage with a Cluster of Databases

Our objective is a scalable infrastructure for information retrieval (IR) with up-to-date retrieval results in the presence of updates. Timely processing of updates is important with novel application domains such as e-commerce. These issues are challenging, given the additional requirement that the system must scale well. We have built PowerDB-IR, a system that has the characteristics sought. This article describes its design, implementation, and evaluation. We follow a three-tier architecture with a database cluster as the bottom layer for storage management. The rationale for a database cluster is to scale out, i.e., to add further cluster nodes, whenever necessary for better performance. The middle tier provides IR-specific retrieval and update services. We deploy state-of-the-art middleware software to coordinate the cluster and to invoke IR-specific components. PowerDB-IR extends the middleware layer with service decomposition and parallelisation. PowerDB-IR has the following features: It supports state-of-the-art retrieval models such as vector space retrieval. It allows documents to be inserted and retrieved concurrently and ensures up-to-date retrieval results with almost no overhead. PowerDB-IR ensures the correctness of global concurrency and recovery. Alternative physical data organisation schemes and respective query processing techniques provide adequate performance for different workloads and database sizes. Scaling out the database cluster yields higher throughput and lower response times. We have run extensive experiments with PowerDB-IR using several commercial database systems as well as different middleware products. Further experiments have quantified the effect of transactional guarantees on performance. The main result is that PowerDB-IR shows surprisingly good scalability and low response times.     

Using a recurrent artificial neural network for dynamic self-adaptation of cluster-based web-server systems

To process huge requests issued from web users, web servers often set up a cluster using switches and gateways where a switch directs users’ requests to some gateway. Each gateway, which is connected to some servers, is considered for processing a specific type of request such as fttp or http service. When servers of a gateway are saturated and the gateway is not able to process more requests, adaptation is performed by borrowing a server from another gateway. However, such a reactive adaptation causes some problems. However, due to problem of the reactive techniques, predictive ones have been paid attention. While a reactive adaptation aims to redress the system after incurring a bottleneck, a predictive adaptation tries to prevent the system from entering the bottleneck. In this article, we improved our previous predictive framework using a Recurrent Artificial Neural Network (RANN) called Nonlinear Autoregressive with eXogenous (external) inputs (NARX). We employed our new framework for adaptation of a web-based cluster where each cluster is meant for a specific service and self-adaptation is used for load balancing clusters. To show the improvement, we used the case study presented in our previous study.     

一种移动Adhoc网络分簇算法及性能分析

提出了一种新的Ad hoc网络分簇路由算法.该算法引入异常度的概念,根据异常度判断何时启动簇结构调整,如何使原簇中保留较多的节点,提高分簇结构稳定性.分析及实验表明,该分簇算法具有簇首的更换频率低和高稳定性的特点.     

能量均衡的无线传感器网络节点非均匀分布路由协议

针对现有无线传感器网络(WSN)分簇路由协议因节点分布不均匀而造成能量不均衡、“热区”能量空洞问题,提出一种能量均衡的节点非均匀分布路由协议。该协议以节点“度”、 节点到Sink节点的距离及节点平均剩余能量与节点本身剩余能量的比值作为竞选主(副)簇头的参数,并且各簇之间通过路由树与Sink节点通信。仿真结果表明,本协议可降减少于“热区”内或节点密度高的簇的簇头轮换次数,推迟出现第一个死亡节点的时间,使网络负载更加均衡,延长了网络的生命周期。