Optimal checkpointing interval of a communication system with rollback recovery

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

Reliability consideration of a mobile communication system with network congestion

SummaryCheckpoint‐based fault‐tolerant (FT) methods have been widely used to enhance the reliability of stream processing systems, but a checkpointing process usually introduces considerable overhead. It is a critical issue to choose the optimal checkpoint interval (OCI) that maximizes the processing efficiency. Traditional OCI models consider the recovery time equals to the execution time from the last checkpoint to the failure moment. However, for stream processing jobs, the recovery time is related to reprocessing workloads, depending on the real‐time input data before a failure. A new model is needed to choose the OCI for stream processing applications. Moreover, the input data rate of a stream processing job fluctuates over time. To solve these problems, we present a novel DSPS OCI (DOCI) model in this paper. We prove that it maximizes the processing efficiency for a given time. We propose an approach to dynamically adjust the OCI for an application to accommodate the workload fluctuations. We conduct simulation experiments to verify the effectiveness of our DOCI model and the efficiency of the online OCI adjustment algorithm. Experimental results with a real‐world dataset show that DOCI achieves an improvement on system efficiency by up to 32%, compared with existing FT approaches.

This paper proposes a novel method for achieving a distributed self-refined fault tolerance by dynamically partitioning the processes into smaller groups, which are mutually disjoint and collectively exhaustive of the whole system. The present model provides tolerance for frequent faults, makes the roll back recovery simple and less time consuming. An optimal checkpoint interval is found using a mathematical approximation and a spare process is made to capture all the in-transit messages when a process fails at its ends. Piggybacking the events of dependent processes on the outgoing messages is used for process grouping. A process with maximum information can scatter chunk values to the other dependent processes in its group. Each process constructs a checkpoint when the received chunk matches with its log.

Processor Allocation and Checkpoint Interval Selection in Cluster Computing Systems

Efficient modeling and optimizing of checkpointing in concurrent component-based software systems

On the impact of process replication on executions of large-scale parallel applications with coordinated checkpointing

Modern communications systems utilize effective encoding plans, multiple-input multiple-output (MIMO) and high-order QAM-constellations for improves spectral efficiency. However, as the dimensions of the system grow, the design of efficient and low-complexity MIMO receivers possesses technical difficulties. Here in this paper, we have demonstrated data reduction method using Principal Component Analysis (PCA) to fuse the data at sensor level at the transmitter and regress the same at the receiver for improvising the channel capacity of the system. We have fused 45 signals sensor data having a bandwidth from 100Hz - 3000Hz which is sampled at 6000 Hz each. The regression is measured using the RMSE of the transmitted and received signals. Also, the communication system has demonstrated the performance of the 2, 4, 8QAM modulation technique with and without LDPC decoder(log-domain) for 2x2, 3x3, 4x4 Multiple Input Multiple Output(MIMO) channel for Bit Error Rate (BER). The performance parameters for data regression and communication error is evaluated over AWGN channel ranging from -15dB to 40dB SNR. The proposed system useful for the next generation low bandwidth communication system such as wireless systems developments, i.e., WiMAX and 4G, 5G, 6G.

Virus tests to maximize availability of software systems

Resilient concurrency control in distributed database systems : Bharat Bhargawa. IEEE Trans. Reliab.R-32 (5), 437 (1983)

Introduction: a communication system is an integral part of any control system, which includes subsystems for diagnostics, monitoring and control of its condition. The imperfection of control modern means, diagnostics and monitoring leads to a situation where decision support systems and decision makers carry out their activities in conditions of uncertainty. The process of making a decision and responding to a change in the state of the system due to the influence of various factors can lead to the failure of the system to fulfill its tasks. To effectively solve this problem, the control system must constantly have reliable information about the state of its elements, and the decision support system for the state of the elements must predict the process of functioning of the communication system. The purpose of the study: to develop an approach to monitoring the functioning of the communication system, which allows obtaining reliable and timely information about the controlled object, as well as identifying and responding in a timely manner to deviations from the stable functioning of the communication system. Methods: using the process approach and the mathematical apparatus of the theory of hierarchical decisions to formalize the functioning of the communication system and form the profile of the communication system. Results: an approach for describing a communication system is proposed, including the tasks and functions of the system. Based on the needs of communication and control systems, a profile of the communication system functioning is formed, which is compared with the functioning process profile of the communication system formed in the process of the communication system functioning. The results of the comparison show the presence of conflicts caused by the influence of various destabilizing factors, the conditions of a changing environment and the control actions of a higher management system. The results obtained are used to form the field of decisions required by decision makers. Practical significance: the results of the study can be used in the design and construction of control systems, diagnostics and monitoring of the state of the communication system. The proposed approach can be used to control the fulfillment of tasks and functions of the communication system during its operation.

Checkpointing and roll-back recovery is a well known technique for recovering from software process failures. Analytical models have been developed for computing the completion time of processes that use various checkpointing strategies such as periodic checkpointing, random checkpointing etc. In this paper, we show that with active replication of processes, a strategy that uses a mechanism we call checkpoints-on-demand will result in an expected completion time smaller than that can be achieved with traditional schemes that use periodic checkpoints. With checkpoints-on-demand, when a process fails, it is recovered from an induced checkpoint taken of a replica of the process. Recovery of persistent server processes through state-transfer from a replica has been proposed in the context of group communication systems and in the process cloning approach of the Delta-4 architecture. But it has not been previously proposed and analyzed as a mechanism for reducing the expected completion time of a long running process.

ObjectivesTo investigate what healthcare professionals perceived and experienced as key patient safety concerns in Bhutan’s healthcare system.DesignQualitative exploratory descriptive inquiry.SettingsThree different levels of hospitals, a training institute and the Ministry...

Fractional Brownian Motions, Fractional Noises and Applications

Measurements from the electrical network are generally transmitted towards the control centres using special communication links. These measurements allow determining the state of the network in real time. However, these measurements often contain uncertainties due to the meter and communication errors, incomplete metering or unavailability of some of these measurements, etc. This paper presents the application of the Particle Swarm Optimization (PSO) algorithm in minimizing the raw measurement errors in order to identify or estimate the optimal operating state of the power system. Two different objective function formulations are assessed by PSO. The first formulation is the Weighted Least Square (WLS) and the second one is the Iteratively Reweighted Least Squares (IRLS) implementation of the Weighted Least Absolute Value (WLAV). Both solutions are compared with a Newton-Raphson (NR) power flow solution using an IEEE 6-bus test system.