Windows NT进程检查点系统NTckpt的设计与实现

设置进程检查点是保存和恢复进程运行状态的重要技术，是实现客错、卷回调试和进程迁移的重要手段。介绍了Windows NT操作系统的进程状态，以及基于该操作系统的进程检查点系统NTckpt的实现原理。NT ckpt实现了完全一致恢复用户地址空间，保汪了地址空间中动态分配数据区域的正确恢复。     

一种基于行为特征的文件检查点优化策略

检查点机制是高性能计算平台的一项重要特性。它能够在程序运行的某一时刻保存程序的运行状态,并在系统故障后恢复程序状态继续执行。由于文件操作在应用程序中的普遍性,支持文件回卷对于检查点技术来说是十分必要的。文件数据备份可以使文件在回卷后恢复到正常状态,但是开销太大。本文提出了一种基于行为特征的文件检查点优化策略(BBFC),能够提供文件数据的正确恢复,有效保证了程序回卷恢复到上一个检查点时文件状态与进程其它状态保持一致。BBFC对文件行为特征进行分类,并根据这些行为特征采取相应的保存恢复策略,从而在很大概率上减少了检查点间隔需要保存的文件内容,降低了文件检查点的时间、空间开销。它对用户透明,简单易用。     

NS-2检查点的实现与性能分析

检查点是一种重要的系统容错机制,可以对运行进程的状态进行保存与恢复.本文通过链接Condor系统的检查点库,在网络模拟器NS-2中实现了用户级透明检查点.提高了NS-2的容错能力,以及在长时间模拟方面的性能.并通过特定网络模拟场景中的实验测试,对网络拓扑中节点、链路的数量对检查点时空开销的影响进行了分析.     

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。     

PDES中乐观时间同步的时空损耗研究

并行离散事件仿真对复杂大规模动态系统的研究以及探索其长远的应用提供了便利，近年来日益成为研究的热点。然而时间同步管理是影响并行离散事件仿真系统高效运行的重要因素之一。乐观的同步是采用检测和回退机制，允许逻辑进程积极的处理本地事件。一旦出现同步错误则利用回退机制从错误中恢复到较早状态，然后再恢复执行。这一切都是通过基于检查点状态保存重建机制来实现的，因而状态保存及状态重建必然伴随着时间和空间的损耗。该文深入研究了在乐观同步机制下，仿真执行时间和内存空间的损耗与检查点间隔之间的关系，并通过推理计算给出了检查点间隔的最优取值范围。     

分布式系统中的检查点算法

检查点能够保存和恢复程序的运行状态．它在进程迁移、容错、卷回调试等领域都有重要的应用．本文对分布式系统中的检查点算法进行了详细的分类评述．检查点算法可分为单进程和分布式程序检查点算法，分布式程序检查点算法又可分为异步检查点算法和一致检查点算法．同时本文系统介绍了改进检查点算法性能的典型方法．这些改进算法主要采用两个策略来减少算法的开销与延迟：一是减少检查点文件中需要存储的信息量，如增量算法等；二是提高检查点操作与目标程序运行的并行性，如主存算法等．最后，文章讨论了目前检查点算法的局限性和进一步的工作．     

Libckpt：一个UNIX环境下的检查点工具

检查点是一种用于回溯和恢复的技术，执行程序的状态每隔一段时间被保存到磁盘文件中，用来进行错误时的恢复，近来一系列减少检查点文件写开销的技术得到发展，本文将介绍Ｌｉｂｃｋｐｔ，一个基于ＵＮＩＸ环境的可移植的检查点工具。Ｌｉｂｃｋｐｔ一方面可以对用户完全透明，一方面也支持直接向用户的检查点生成，这种直接面向用户的方式是Ｌｉｂｃｋｐｔ的一大改进。     

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。     

Linux中检查点(Checkpoint)的核心支持——ckpt文件系统的设计

检查点(Checkpoint)是一种软件容错机制,它的目的是提高系统可靠性、减少运算损失,同时检查点机制也是并行系统中进程迁移和负载平衡的基础。在一些检查点系统中,由于对进程的状态检查/状态恢复只具有用户级支持,所以有许多局限性,比如不能完成进程外部状态检查。而在作者的设计与实现中由于具有了核心级的支持,所以能够充分地克服这些局限性。     

Linux下系统V共享内存的保存与恢复

设置检查点是保存和恢复进程运行状态的一种重要技术,是实现容错、卷回调试和进程迁移的重要手段。本文研究了全透明检查点系统Epckpt在系统Ⅴ共享内存方面的实现方法和不足,给出了自己的改进,从而更好地实现了系统Ⅴ共享内存的保存与恢复。     

Diskless checkpointing

Diskless Checkpointing is a technique for checkpointing the state of a long-running computation on a distributed system without relying on stable storage. As such, it eliminates the performance bottleneck of traditional checkpointing on distributed systems. In this paper, we motivate diskless checkpointing and present the basic diskless checkpointing scheme along with several variants for improved performance. The performance of the basic scheme and its variants is evaluated on a high-performance network of workstations and compared to traditional disk-based checkpointing. We conclude that diskless checkpointing is a desirable alternative to disk-based checkpointing that can improve the performance of distributed applications in the face of failures     

Adaptive Task Checkpointing and Replication: Toward Efficient Fault-Tolerant Grids

A grid is a distributed computational and storage environment often composed of heterogeneous autonomously managed subsystems. As a result, varying resource availability becomes commonplace, often resulting in loss and delay of executing jobs. To ensure good grid performance, fault tolerance should be taken into account. Commonly utilized techniques for providing fault tolerance in distributed systems are periodic job checkpointing and replication. While very robust, both techniques can delay job execution if inappropriate checkpointing intervals and replica numbers are chosen. This paper introduces several heuristics that dynamically adapt the above mentioned parameters based on information on grid status to provide high job throughput in the presence of failure while reducing the system overhead. Furthermore, a novel fault-tolerant algorithm combining checkpointing and replication is presented. The proposed methods are evaluated in a newly developed grid simulation environment dynamic scheduling in distributed environments (DSiDE), which allows for easy modeling of dynamic system and job behavior. Simulations are run employing workload and system parameters derived from logs that were collected from several large-scale parallel production systems. Experiments have shown that adaptive approaches can considerably improve system performance, while the preference for one of the solutions depends on particular system characteristics, such as load, job submission patterns, and failure frequency.     

An efficient checkpointing method for multicomputers with wormhole routing

Efficient checkpointing and resumption of multicomputer applications is essential if multicomputers are to support time-sharing and the automatic resumption of jobs after a system failure. We present a checkpointing scheme that is transparent, imposes overhead only during checkpoints, requires minimal message logging, and allows for quick resumption of execution from a checkpointed image. Furthermore, the checkpointing algorithm allows each processorp to continue running the application being checkpointed except during the time thatp is actively taking a local snapshot, and requires no global stop or freeze of the multicomputer. Since checkpointing multicomputer applications poses requirements different from those posed by checkpointing general distributed systems, existing distributed checkpointing schemes are inadequate for multicomputer checkpointing. Our checkpointing scheme makes use of special properties of wormhole routing networks to satisfy this new set of requirements.     

可靠的分布式系统生存性保障模型

基于检查点的协同式回滚恢复机制是一种针对分布式系统生存性保障的有效机制,现有分布式系统中基于检查点的回滚恢复机制以分布式信道可靠作为假设前提,而实际应用场景中,该假设并不总是成立。针对分布式系统实际的应用环境,提出了适用于信道不可靠的分布式计算环境的协同式系统生存性保障模型。该模型在保留检查点回滚恢复机制优点的基础上,通过建立冗余通信链路和进程迁移来保障不可靠通信信道环境下分布式系统的生存性。     

A debugger for distributed programs

Developing a distributed debugger is much more complex than developing a sequential debugger. This added complexity is mainly due to the non-determinism of events that communication delays introduce into distributed systems. We explore the problems that one must address when designing a distributed program debugger and then describe our design and implementation of DPD (distributed program debugger). Problems addressed include non-determinism of events, finding consistent system states, setting breakpoints, recording events, and checkpointing. Important features of DPD include dynamic roll back and replay, as well as a graphical user interface. DPD has been tested successfully in debugging distributed programs within a distributed facility called REM (remote execution manager).     

Unix进程检查点设置关键技术

Unix进程的检查点设置是实现分布/并行系统容错、重播调试、进程迁移、系统模拟和作业切换等功能的基础。该论文主要论述UNIX进程检查点基本信息的保存与恢复、文件检查点、检查点信息的优化等关键技术,最后介绍Libckpt、Condor以及自行设计的Libcsm等检查点设置工具。     

A Survey of Distributed Database Checkpointing

Checkpointing a database is a vital technique to reduce the recovery time in the presence of a failure. For distributed databases, checkpointing also provides an efficient way to perform global reconstruction. In this paper, we survey and classify previous approaches for checkpointing a distributed database. Since the need for global reconstruction is infrequent in most distributed databases, a less restrictive and less resource-consuming approach to checkpoint distributed databases in an integrated distributed database system is recommended over a transaction consistent checkpoint approach. For a federated or multidatabase system, any type of global consistent checkpoint is difficult to achieve without violating local autonomy.     

Modeling of hierarchical distributed systems with fault-tolerance

Since each of the levels in a hierarchical system could have various characteristics, different fault-tolerant schemes could be appropriate at different levels. A stochastic Petri net (SPN) is used to investigate various fault-tolerant schemes in this context. The basic SPN is augmented by parameterized subnet primitives to model the fault-tolerant schemes. Both centralized and distributed fault-tolerant schemes are considered. The two schemes are investigated by considering the individual levels in a hierarchical system independently. In the case of distributed fault tolerance, two different checkpointing strategies are considered. The first scheme is called the arbitrary checkpointing strategy. Each process in this scheme does its checkpointing independently; thus, the domino effect may occur. The second scheme is called the planned strategy. Here, process checkpointing is constrained to ensure no domino effect. The results show that, under certain conditions, an arbitrary checkpointing strategy can perform better than a planned strategy. The effect of integration on the fault-tolerant strategies of the various levels of a hierarchy are studied     

A Low-Cost Checkpointing Technique for Distributed Databases

For distributed databases, checkpointing is used to ensure an efficient way to perform global reconstruction. However, the need for global reconstruction is infrequent. Most current checkpointing approaches for distributed databases are too expensive during run time. Some of them allow the checkpointing process to run in parallel with normal transactions at the cost of more data and resource contention, which in turn causes longer response time for normal transactions. Thus, an efficient way to checkpoint distributed databases is needed to avoid degrading the system performance. This paper presents a low-cost solution, called Loosely Synchronized Local Fuzzy Checkpointing (LSLFC), to these problems. LSLFC supports global reconstruction, and our performance study shows that LSLFC has little overhead during run time.