实时双机系统中检查点设置周期的选择

为了保证长运行时间软件的实时性要求,本文针对双机冗余系统,采用检查点设置与卷回恢复的方法提出了一种系统模型,同时为使任务的完成时间最短而给出了如何确定检查点设置周期的方法。文章最后进行了数学分析并给出了模拟结果比较。     

具有O(n)消息复杂度的协调检查点设置算法

协调检查点设置及回卷恢复技术作为一种有效的容错手段,已广泛地运用在集群等并行/分布计算机系统中.为了进一步降低协调检查点设置的时间和空间开销,提出了一种基于消息计数的协调检查点设置算法.该算法无须对底层消息通道的FIFO特性进行假设,并使同步阶段引入的控制消息复杂度由通常的O(n2)降低到O(n),有效地提高了系统的效率和扩展性.     

具有O(n)消息复杂度的协调检查点设置算法

协调检查点设置及回卷恢复技术作为一种有效的容错手段,已广泛地运用在集群等并行/分布计算机系统中.为了进一步降低协调检查点设置的时间和空间开销,提出了一种基于消息计数的协调检查点设置算法.该算法无须对底层消息通道的FIFO特性进行假设,并使同步阶段引入的控制消息复杂度由通常的O(n²)降低到O(n),有效地提高了系统的效率和扩展性.     

基于机群系统的PVM并行编程技术研究

首先简单介绍了当今最流行的分布式并行编程环境之一－PVM系统;然后论述了基于机群系统的PVM编程的一般方法,详细讨论了计算任务的分解,程序模式的选择,进程同步的设置及消息传递等关键步骤,最后,对PVM程序的调试作了简单的探讨。     

基于PVM的准同步检查点设置方法

检查点是并行系统中实现容错的重要手段,同步检查点方法已广泛应用在工作站机群系统中。PVM所提供的消息传递机制支持高效的异构网络计算,但不支持客错功能。为了降低同步检查点设置的时间开销,提出了一种基于PVM的准同步检查点设置方法,它吸取了同步检查点方法的优点,又通过消息记录方式实现各节点间独立进行状态保存,大大降低了检查点的同步开销,提高了检查点操作效率,该方法在PVM环境下得以实现,实验结果表明所提出的方法具有较好的客错性能。     

一种低开销非阻塞的协同式检查点算法

协同式检查点设置及卷回恢复技术是一种简单有效的容错手段,被广泛地运用于并行/分布式系统中。为进一步降低协同式检查点算法的开销,该文给出了一个基于可重建检查点的非阻塞协同式检查点算法。并行程序出错导致卷回恢复发生的概率远小于检查点设置概率,该算法利用这一特性,将检查点设置的部分开销转至卷回恢复阶段,降低了容错的开销,提高了系统的可扩展性。     

一种降低并行程序检查点开销的方法

检查点设置和卷回恢复是提高系统可靠性和实现容错计算的有效途径,其性能通常用开销率来评价,而检查点开销是影响开销率的主要因素。针对目前并行程序运行时存在较多通信阻塞时间的现状,该文在写时复制检查点缓存的基础上提出了一种进一步降低检查点开销的方法。通过控制状态保存线程的调度和选择合适的状态保存粒度,该方法能很好地利用通信阻塞时间隐藏状态保存线程运行时带来的开销,从而能进一步降低开销率。     

MPP机检查点系统的设计与实现

检查点技术是一种回溯和恢复的技术，在并行应用环境中，作用尤为突出。它定期保存程序的运行状态，以便需要时能及时从中恢复。本文系统介绍了检查点技术的基本概念和实现细节，详细阐述了ＭＰＰ机检查点系统的设计思想，探讨了其中的主要问题－检查点的状态一致性以及检查点的性能优化措施。本文的结论是：我们能够在ＭＰ系统中实现高效的检查点技术，以此来提高此类系统的可用性。     

基于虚拟文件操作的文件检查点设置

实现分布/并行系统容错的基础是单进程检查点设置和卷回恢复技术,而对活动文件信息进行保存和恢复则是这种技术的重要方面.提出一种虚拟文件操作策略,实现了对用户文件的检查点设置,有效地解决了发生故障时用户文件内容与进程全局状态的不一致的问题.该方法通过文件块式管理、检查点分布操作等技术,使得在空间开销、正常运行时间、恢复时间等性能指标上优于其他方法,并且具有对用户透明、可最大限度地保留已完成工作的特点.     

基于PVM的并行调试环境

并行软件开发环境的研究已日益成为并行计算和并行处理的重点。本文简介了可移植的消息传递环境ＰＶＭ，讨论了以此为目标的图形监视环境ＸＰＶＭ，阐明ＸＰＶＭ环境与实际需要的ＰＶＭ并行调试环境之间的差距，并在此基础上探讨了并行调试环境开发中的技术难点及其设计要求。     

A fully informed model-based checkpointing protocol for preventing useless checkpoints

Checkpointing and rollback recovery are widely used techniques for handling failures in distributed systems. When processes involved in a distributed computation are allowed to take checkpoints independently without any coordination with each other, some or all of the checkpoints taken may not be part of any consistent global checkpoint, and hence, are useless for recovery. Communication-induced checkpointing algorithms allow processes to take checkpoints independently and also ensure that each checkpoint taken is part of a consistent global checkpoint by forcing processes to take some additional checkpoints. It is well known that it is impossible to design an optimal communication-induced checkpointing algorithm (i.e. a checkpointing algorithm that takes minimum number of forced checkpoints). So, researchers have designed communication-induced checkpointing algorithms that reduce forced checkpoints using different heuristics. In this paper, we present a communication-induced checkpointing algorithm which takes less number of forced checkpoints when compared to some of the existing checkpointing algorithms in its class.     

A survey and review of the current state of rollback‐recovery for cluster systems

A variety of research problems exist that require considerable time and computational resources to solve. Attempting to solve these problems produces long‐running applications that require a reliable and trustworthy system upon which they can be executed. Cluster systems provide an excellent environment upon which to run these applications because of their low cost to performance ratio; however, due to being created using commodity components they are prone to failures. This report surveyed and reviewed the issues currently relating to providing fault tolerance for long‐running applications. Several fault tolerance approaches were investigated; however, it was found that rollback‐recovery provides a favourable approach for user applications in cluster systems. Two facilities are required to provide fault tolerance using rollback‐recovery: checkpointing and recovery. It was shown here that a multitude of work has been done for enhancing checkpointing; however, the intricacies of providing recovery have been neglected. The problems associated with providing recovery include; providing transparent and autonomic recovery, selecting appropriate recovery computers, and maintaining a consistent observable behaviour when an application fails. Copyright © 2009 John Wiley & Sons, Ltd.     

A New Approach for High Performance Computing Systems with Various Checkpointing Schemes

Roll-forward recovery schemes were proposed to enhance the performance of fault tolerant systems employing checkpointing approach. In the roll-forward schemes, multiple processors are used for simultaneous roll-forward and validation processing. This paper proposes the sample comparison approach along with the checkpointing, which further improves the performance by reducing the overhead imposed by the checkpointing. We also develop general analytical models for estimating the availability, which are applicable for any checkpointing scheme. Performance comparisons reveal that the availabilities of the checkpointing schemes with sample comparison are higher than those of the schemes without it, while the required checkpoint interval is larger.     

Memory exclusion: optimizing the performance of checkpointing systems

Checkpointing systems are a convenient way for users to make their programs fault‐tolerant by intermittently saving program state to disk and restoring that state following a failure. The main concern with checkpointing is the overhead that it adds to running time of the program. This paper describes memory exclusion, an important class of optimizations that reduce the overhead of checkpointing. Some forms of memory exclusion are well‐known in the checkpointing community. Others are relatively new. In this paper, we describe all of them within the same framework. We have implemented these optimization techniques in two checkpointers: libckpt , which works on Unix‐based workstations, and CLIP , which works on the Intel Paragon. Both checkpointers are publicly available at no cost. We have checkpointed various long‐running applications with both checkpointers and have explored the performance improvements that may be gained through memory exclusion. Results from these experiments are presented and show the improvements in time and space overhead. Copyright © 1999 John Wiley & Sons, Ltd.     

多米诺效应的解决策略研究

定义了备查点间隔之间的先于关系，并对分布式系统执行的语义正确性进行了约束，证明了逆时先于现象是产生多米诺效应的本质，提出了多米诺避免、多米诺检测与消除、多米诺容忍三大解决策略.     

一种基于信道不可靠环境的协调式检查点协议

在分布式计算环境中经常使用检查点／恢复策略来进行容错。文中主要研究在信道不可靠的环境中通过协调使相互通信的各进程所做的检查点保持全局一致性的方法。通过分析中途消息与信道可靠性之闯的关系以及已有检查点协议对于中途消息处理方法,提出了一种应用于信道不可靠环境下的协调式检查点方法,其消息复杂度为O（N）且不引入其他的计算负担,只通过一次同步即可达到全局一致性状态,相比于以往的协调式检查点协议大大减小了时间开销,提高了在不可靠信道环境中做全局一致检查点的效率。     

Reliable user‐level rollback recovery implementation for multithreaded processes on windows

The existing user‐level checkpointing schemes support only a limited portion of multithreaded programs because they are derived from the schemes for single‐threaded applications. This paper addresses the impact of thread suspension point on rollback recovery, and presents a checkpointing scheme for multithreaded processes. Unlike the existing schemes in which the checkpointer suspends every working thread, our scheme employs a distinctive strategy that every working thread suspends itself. This technique manages to avoid the suspension point in the API code or kernel code, ensuring correct rollback recovery. Our scheme supports inter‐thread synchronization and thread lifetime. Copyright © 2006 John Wiley & Sons, Ltd.