Optimal Checkpoint Interval Research Articles

Analytical Model on Hybrid State Saving with a Limited Number of Checkpoints and Bound Rollbacks

This paper discusses distributed checkpointing with logging for practical applications running with limited resources. We present a discrete time model evaluating the total expected overhead per event where the number of available checkpoints that each process can hold is finite. The rollback distance is also bound to some finite interval in many actual applications. Therefore, the recovery overhead for the checkpointing scheme is described by using a truncated geometric distribution as the rollback distance distribution. Although it is difficult to analytically derive the optimal checkpoint interval, which minimizes the total expected overhead, substituting other simple probabilistic distributions instead of the truncated geometric distribution enables us to do this explicitly. Numerical examples obtained through simulations are presented to show that we can achieve almost minimized total overhead by using the new models and analyses.

Optimal checkpointing interval for two-level recovery schemes

It is important to design computer systems to tolerate some failures. This paper proposes two-level recovery schemes, soft checkpoint (SC) and hard checkpoint (HC), which are useful to recover from failures. Soft checkpoint is less reliable and less overhead than those of HC, and is set up between HCs to reduce the overhead of the process. The total expected overhead of one cycle from HC to HC is obtained, using Markov renewal processes, and an optimal interval which minimizes it is computed. It is shown in a numerical example that a two-level recovery scheme can achieve a good performance.

Reliability consideration of a mobile communication system with network congestion

High quality traffic for networks is urgently needed for mobile communication systems. Mobile stations frequently become unavailable due to communication errors generated by network congestion. Traffic congestion in a network system may occur intermittently and continue for a length of time, sometimes causing communication errors. If congestions happens during communication, communication errors occur and the communication is rejected. This paper considers the problem of reliability in mobile communication systems during congestion by using a recovery scheme. We formulate a stochastic model of a mobile communication system which consists of mobile stations, several base stations and a switching center. When communication errors occur, the system makes a rollback recovery and returns to the recent checkpoint. We derive the mean time to take checkpoint and the expected number of rollback recoveries, handoff, and successful transmissions until communication errors occur. Further, we calculate the expected costs and discuss ways to minimize the costs by analyzing the optimal checkpoint intervals.

Optimal checkpointing interval of a communication system with rollback recovery

This paper considers a communication system which consists of many processors and studies the problem for improving its reliability by adopting the recovery techniques of checkpoint and rollback. When either processor failure or communication error has occurred, the rollback recovery for processors associated with such an event is executed to the most recent checkpoint, and so, a consistent state in the whole system is maintained. The stochastic model with the above recovery techniques is formulated, using the theory of Markov renewal processes. The mean time to take checkpoint and the expected numbers of rollback recovery caused by processor failures and communication errors are derived. Further, an optimal checkpointing interval which minimizes the expected cost is analytically discussed.

Processor Allocation and Checkpoint Interval Selection in Cluster Computing Systems

Performance prediction of checkpointing systems in the presence of failures is a well-studied research area. While the literature abounds with performance models of checkpointing systems, none addresses the issue of selecting runtime parameters other than the optimal checkpointing interval. In particular, the issue of processor allocation is typically ignored. In this paper, we present a performance model for long-running parallel computations that execute with checkpointing enabled. We then discuss how it is relevant to today's parallel computing environments and software, and present case studies of using the model to select runtime parameters.

Rollback recovery for a communication system with two failure states

As computer communication technology has developed, system control mechanisms have been realized by a number of processors, and, hence, it has become necessary to carry out processing distributively and rapidly. Also, as the system mechanisms have become increasingly complicated, the problems of improving reliability and increasing capabilities have become important. In this paper, we consider a control system which is roughly divided into one mark processor and a group of other processors, and formulate a stochastic model by taking notice of only communications between two processors. We perform scheduled checkpointing and execute rollback recovery to restore the consistency of a whole system when two faults of processor failures and communication errors have occurred. The expected cost is obtained and an optimal checkpoint interval which minimizes it is discussed. © 2001 Scripta Technica, Electron Comm Jpn Pt 3, 84(9): 49–55, 2001

Rollback recovery for a communication system with two failure states

AbstractAs computer communication technology has developed, system control mechanisms have been realized by a number of processors, and, hence, it has become necessary to carry out processing distributively and rapidly. Also, as the system mechanisms have become increasingly complicated, the problems of improving reliability and increasing capabilities have become important. In this paper, we consider a control system which is roughly divided into one mark processor and a group of other processors, and formulate a stochastic model by taking notice of only communications between two processors. We perform scheduled checkpointing and execute rollback recovery to restore the consistency of a whole system when two faults of processor failures and communication errors have occurred. The expected cost is obtained and an optimal checkpoint interval which minimizes it is discussed. © 2001 Scripta Technica, Electron Comm Jpn Pt 3, 84(9): 49–55, 2001

Impact of checkpoint latency on overhead ratio of a checkpointing scheme

Checkpointing reduces loss of computation in the presence of failures. Two metrics characterize a checkpointing scheme: checkpoint overhead and checkpoint latency. The paper shows that a large increase in latency is acceptable if it is accompanied by a relatively small reduction in overhead. Also, for equidistant checkpoints, optimal checkpoint interval is shown to be typically independent of checkpoint latency.

Comparative analysis of periodic state saving techniques in time warp simulators

Checkpointing in a time warp synchronized parallel simulator is a necessary and potentially expensive operation. In the simple case, a time warp simulator checkpoints every χ events, for some fixed value χ. For larger values of χ, the simulator requires less overhead for saving the state, but incurs an increased latency during rollback. Thus, the problem is to balance the time to save states against the time to coast forward upon rollback. Unfortunately, a static determination of a optimal value for χ is very difficult and can vary widely, even between closely related instances of a time warp simulator. Furthermore, the optimal checkpoint interval may actually vary over the lifetime of the simulation. To address these problems, several investigators have proposed dynamically adjusting the checkpoint interval χ as the simulation progresses. This paper analyzes three previous techniques for dynamically sizing checkpoint intervals and presents a new, heuristic algorithm for this purpose. All four techniques are implemented in a common application domain (digital system simulation from VHDL descriptions) and a direct comparison between the algorithms is performed. The results show a significant difference in the performance of the implemented algorithms. However, in virtually all cases, the dynamic algorithms performed near or better than the best static value. Furthermore, the best algorithms performed as much as 12% better than the best static value.

Selecting the checkpoint interval in time warp simulation

In Time Warp parallel simulation, the state of each process must be saved (checkpointed) regularly in case a rollback is necessary. Although most existing Time Warp implementations checkpoint after every state transition, this is not necessary, and the checkpoint interval is in reality a tuning parameter of the simulation. Lin and Lazowska[6] proposed a model to derive the optimal checkpoint interval by assuming that the rollback behavior of Time Warp is not affected by the frequency of checkpointing. An experimental study conducted by Preiss et al.[10] indicates that the behavior of rollback is affected by the frequency of checkpointing in general, and that the Lin-Lazowska model may not reflect the real situations in general. This paper extends the Lin-Lazowska model to include the effect of the checkpoint interval on the rollback behavior. The relationship among the checkpoint interval, the rollback behavior, and the overhead associated with state saving and restoration is described. A checkpoint interval selection algorithm which quickly determines the optimal checkpoint interval during the execution of Time Warp simulation is proposed. Empirical results indicate that the algorithm converges quickly and always selects the optimal checkpoint interval.

An analytical comparison of periodic checkpointing and incremental state saving

The successful application of optimistic synchronization techniques in parallel simulation requires that rollback overheads be contained. The chief contributions to rollback overhead in a Time Warp simulation are the time required to save state information and the time required to restore a previous state. Two competing techniques for reducing rollback overhead are periodic checkpointing (Lin and Lazowska, 1989) and incremental state saving (Bauer et al., 1991). This paper analytically compares the relative performance of periodic checkpointing to incremental state savings. The analytical model derived for periodic checkpointing is based almost entirely on the previous model developed by Lin (Lin and Lazowska, 1989). The analytical model for incremental state saving has been developed for this study. The comparison assumes an optimal checkpoint interval and shows under what simulation parameters each technique performs best.

On selecting rollback points for error recovery

In a concurrent processing system with recovery blocks, the occurrence of a fault in one process can contaminate the data used by other processes because of interprocess communications. One of the effective techniques to deal with faults in such a system is rollback and recovery with global checkpoints. In global checkpointing, N ( N > 1) checkpoints are maintained, since the faults may not be detected on occurrence. The time required for rollback and recovery depends on the number of checkpoints maintained, the intercheckpoint interval, and the way checkpoints are selected for rollback. This paper discusses the problem of checkpoint selection. A generalized formulation for checkpoint selection is given from which three different schemes are derived. Each scheme is shown to have a smaller expected cost of recovery and a larger optimal checkpoint interval than rolling back to the most recent checkpoint.