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Kishor S Trivedi - One of the best experts on this subject based on the ideXlab platform.

  • maximizing interval reliability in Operational Software system with rejuvenation
    International Symposium on Software Reliability Engineering, 2003
    Co-Authors: H Suzuki, T Dohi, Naoto Kaio, Kishor S Trivedi
    Abstract:

    Software aging often affects the performance of a Software system and eventually causes it to fail. A novel approach to handle transient Software failures is called Software rejuvenation which can be regarded as a preventive and proactive solution that is particularly useful for counteracting the phenomenon of Software aging. In this paper, we consider the optimal Software rejuvenation policy maximizing the interval reliability in the general semi-Markov framework. We derive analytically the optimal Software rejuvenation timing which maximizes the limiting interval reliability or the interval reliability with exponentially distributed operation times. Further, we examine numerically the transient behavior of the interval reliability at an arbitrary operation time. Our results under the interval reliability criteria are extentions of some earlier work, since the interval reliability can be specialized to the pointwise availability and the common reliability function.

  • analysis of inspection based preventive maintenance in Operational Software systems
    Symposium on Reliable Distributed Systems, 2002
    Co-Authors: Kalyanaraman Vaidyanathan, D Selvamuthu, Kishor S Trivedi
    Abstract:

    Recently, the phenomenon of "Software aging", one in which the state of a Software system gradually degrades with time and eventually leads to performance degradation or crash/hang failure, has been reported. Preventive maintenance of Operational Software systems is used specifically to counteract this phenomenon. However preventive maintenance incurs an overhead in terms of downtime and cost and this must be traded off with the cost of failures to obtain maximum benefits. We present an analytical model of a Software system employing inspection-based preventive maintenance, through a Markov Regenerative Process (MRGP) with a subordinated semi-Markov reward process. Furthermore, we consider preemptive-resume type transitions. The model is solved for steady state as well as transient conditions and expressions for expected downtime and expected cost are derived. Numerical examples are presented to illustrate the applicability of the models. With the help of these models, optimal strategies for preventive maintenance techniques such as "Software rejuvenation" could be formulated.

  • modeling and analysis of Software aging and rejuvenation
    Annual Simulation Symposium, 2000
    Co-Authors: Kishor S Trivedi, Kalyanaraman Vaidyanathan, Katerina Gosevapopstojanova
    Abstract:

    Software systems are known to suffer from outages due to transient errors. Recently, the phenomenon of "Software aging", one in which the state of the Software system degrades with time, has been reported. To counteract this phenomenon, a proactive approach of fault management, called "Software rejuvenation", has been proposed. This essentially involves gracefully terminating an application or a system and restarting it in a clean internal state. We discuss stochastic models to evaluate the effectiveness of proactive fault management in Operational Software systems and determine optimal times to perform rejuvenation, for different scenarios. The latter part of the paper deals with measurement-based methodologies to detect Software aging and estimate its effect on various system resources. Models are constructed using workload and resource usage data collected from the UNIX operating system over a period of time. The measurement-based models are intended to help development of strategies for Software rejuvenation triggered by actual measurements.

  • a measurement based model for estimation of resource exhaustion in Operational Software systems
    International Symposium on Software Reliability Engineering, 1999
    Co-Authors: Kalyanaraman Vaidyanathan, Kishor S Trivedi
    Abstract:

    Software systems are known to suffer from outages due to transient errors. Recently, the phenomenon of "Software aging", in which the state of the Software system degrades with time, has been reported (S. Garg et al., 1998). The primary causes of this degradation are the exhaustion of operating system resources, data corruption and numerical error accumulation. This may eventually lead to performance degradation of the Software or crash/hang failure, or both. Earlier work in this area to detect aging and to estimate its effect on system resources did not take into account the system workload. In this paper, we propose a measurement-based model to estimate the rate of exhaustion of operating system resources both as a function of time and the system workload state. A semi-Markov reward model is constructed based on workload and resource usage data collected from the UNIX operating system. We first identify different workload states using statistical cluster analysis and build a state-space model. Corresponding to each resource, a reward function is then defined for the model based on the rate of resource exhaustion in the different states. The model is then solved to obtain trends and the estimated exhaustion rates and the time-to-exhaustion for the resources. With the help of this measure, proactive fault management techniques such as "Software rejuvenation" (Y. Huang et al., 1995) may be employed to prevent unexpected outages.

T Dohi - One of the best experts on this subject based on the ideXlab platform.

  • comprehensive evaluation of aperiodic checkpointing and rejuvenation schemes in Operational Software system
    Journal of Systems and Software, 2010
    Co-Authors: H Okamura, T Dohi
    Abstract:

    This paper examines comprehensive evaluation of aperiodic time-based checkpointing and rejuvenation schemes maximizing the steady-state system availability in an Operational Software system. We consider two kinds of maintenance policies: checkpointing prior to rejuvenating (CPTR) and rejuvenating prior to checkpointing (RPTC). These schemes are complementary from each other to schedule checkpoints and rejuvenation points. In addition, under a periodic full maintenance operation, we show that aperiodic checkpointing or rejuvenation scheme is optimal to maximize the steady-state system availability by applying the dynamic programming. In numerical examples, CPTR and RPTC are comparatively examined with same overhead parameters, and the effects of CPTR and RPTC on maximizing the steady-state system availability are investigated.

  • availability optimization in Operational Software system with aperiodic time based Software rejuvenation scheme
    2008 IEEE International Conference on Software Reliability Engineering Workshops (ISSRE Wksp), 2008
    Co-Authors: H Okamura, T Dohi
    Abstract:

    This paper discusses an aperiodic time-based rejuvenation policy maximizing the steady-state system availability in Operational Software system. Under a fixed periodic checkpoint schedule, we develop an algorithm to derive the optimal aperiodic rejuvenation times based on dynamic programming. In numerical examples, the optimal rejuvenation time and its maximum availability are illustrated in the case where the system failure obeys the Weibull distribution.

  • determining the optimal Software rejuvenation schedule via semi markov decision process
    Journal of Computer Science, 2006
    Co-Authors: Hiroyuki Eto, T Dohi
    Abstract:

    Software rejuvenation is a preventive and proactive maintenance policy that is particularly useful for counteracting the phenomenon of Software aging. In this study we consider an Operational Software system with multiple degradations and derive the optimal Software rejuvenation policy minimizing the expected operation cost per unit time in the steady state, via the dynamic programming approach. Especially, we show analytically that the control-limit type of Software rejuvenation policy is optimal. A numerical example is presented to make a decision table and to perform the sensitivity analysis of cost parameters.

  • maximizing interval reliability in Operational Software system with rejuvenation
    International Symposium on Software Reliability Engineering, 2003
    Co-Authors: H Suzuki, T Dohi, Naoto Kaio, Kishor S Trivedi
    Abstract:

    Software aging often affects the performance of a Software system and eventually causes it to fail. A novel approach to handle transient Software failures is called Software rejuvenation which can be regarded as a preventive and proactive solution that is particularly useful for counteracting the phenomenon of Software aging. In this paper, we consider the optimal Software rejuvenation policy maximizing the interval reliability in the general semi-Markov framework. We derive analytically the optimal Software rejuvenation timing which maximizes the limiting interval reliability or the interval reliability with exponentially distributed operation times. Further, we examine numerically the transient behavior of the interval reliability at an arbitrary operation time. Our results under the interval reliability criteria are extentions of some earlier work, since the interval reliability can be specialized to the pointwise availability and the common reliability function.

Kalyanaraman Vaidyanathan - One of the best experts on this subject based on the ideXlab platform.

  • analysis of inspection based preventive maintenance in Operational Software systems
    Symposium on Reliable Distributed Systems, 2002
    Co-Authors: Kalyanaraman Vaidyanathan, D Selvamuthu, Kishor S Trivedi
    Abstract:

    Recently, the phenomenon of "Software aging", one in which the state of a Software system gradually degrades with time and eventually leads to performance degradation or crash/hang failure, has been reported. Preventive maintenance of Operational Software systems is used specifically to counteract this phenomenon. However preventive maintenance incurs an overhead in terms of downtime and cost and this must be traded off with the cost of failures to obtain maximum benefits. We present an analytical model of a Software system employing inspection-based preventive maintenance, through a Markov Regenerative Process (MRGP) with a subordinated semi-Markov reward process. Furthermore, we consider preemptive-resume type transitions. The model is solved for steady state as well as transient conditions and expressions for expected downtime and expected cost are derived. Numerical examples are presented to illustrate the applicability of the models. With the help of these models, optimal strategies for preventive maintenance techniques such as "Software rejuvenation" could be formulated.

  • modeling and analysis of Software aging and rejuvenation
    Annual Simulation Symposium, 2000
    Co-Authors: Kishor S Trivedi, Kalyanaraman Vaidyanathan, Katerina Gosevapopstojanova
    Abstract:

    Software systems are known to suffer from outages due to transient errors. Recently, the phenomenon of "Software aging", one in which the state of the Software system degrades with time, has been reported. To counteract this phenomenon, a proactive approach of fault management, called "Software rejuvenation", has been proposed. This essentially involves gracefully terminating an application or a system and restarting it in a clean internal state. We discuss stochastic models to evaluate the effectiveness of proactive fault management in Operational Software systems and determine optimal times to perform rejuvenation, for different scenarios. The latter part of the paper deals with measurement-based methodologies to detect Software aging and estimate its effect on various system resources. Models are constructed using workload and resource usage data collected from the UNIX operating system over a period of time. The measurement-based models are intended to help development of strategies for Software rejuvenation triggered by actual measurements.

  • a measurement based model for estimation of resource exhaustion in Operational Software systems
    International Symposium on Software Reliability Engineering, 1999
    Co-Authors: Kalyanaraman Vaidyanathan, Kishor S Trivedi
    Abstract:

    Software systems are known to suffer from outages due to transient errors. Recently, the phenomenon of "Software aging", in which the state of the Software system degrades with time, has been reported (S. Garg et al., 1998). The primary causes of this degradation are the exhaustion of operating system resources, data corruption and numerical error accumulation. This may eventually lead to performance degradation of the Software or crash/hang failure, or both. Earlier work in this area to detect aging and to estimate its effect on system resources did not take into account the system workload. In this paper, we propose a measurement-based model to estimate the rate of exhaustion of operating system resources both as a function of time and the system workload state. A semi-Markov reward model is constructed based on workload and resource usage data collected from the UNIX operating system. We first identify different workload states using statistical cluster analysis and build a state-space model. Corresponding to each resource, a reward function is then defined for the model based on the rate of resource exhaustion in the different states. The model is then solved to obtain trends and the estimated exhaustion rates and the time-to-exhaustion for the resources. With the help of this measure, proactive fault management techniques such as "Software rejuvenation" (Y. Huang et al., 1995) may be employed to prevent unexpected outages.

Olivier Bock - One of the best experts on this subject based on the ideXlab platform.

  • the arome wmed reanalyses of the first special observation period of the hydrological cycle in the mediterranean experiment hymex
    Geoscientific Model Development, 2019
    Co-Authors: Nadia Fourrie, Mathieu Nuret, Pierre Brousseau, Olivier Caumont, Alexis Doerenbecher, Eric Wattrelot, Patrick Moll, Herve Benichou, Dominique Puech, Olivier Bock
    Abstract:

    To study key processes of the water cycle, two special observation periods (SOPs) of the Hydrological cycle in the Mediterranean experiment (HyMeX) took place during the autumn 2012 and winter 2013. The first SOP aimed to study high precipitation systems and flash-flooding in the Mediterranean area. The AROME-WMED (West-Mediterranean) model (Fourrie et al., 2015) is a dedicated version of the mesoscale Numerical Weather Prediction (NWP) AROME-France model 5 which covers the western Mediterranean basin providing the HyMeX Operational centre with daily real-time analyses and forecasts. These products allowed adequate decision-making for the field campaign observation deployment and the instrument operation. Shortly after the end of the campaign, a first re-analysis with more observations was performed with the first SOP Operational Software. An ensuing comprehensive second re-analysis of the first SOP which included field research observations (not assimilated in real-time), and some reprocessed observation datasets, was made with AROME-WMED. Moreover, a more recent version of the AROME model was used with updated background error statistics for the assimilation process. This paper depicts the main differences between the real-time version and the benefits brought by HyMeX re-analyses with AROME-WMED. The first re-analysis used 9 % of additional data and the second one 24 % more compared to the real-time version. The second re-analysis is found to be closer to observations than the previous AROME-WMED analyses. The second re-analysis forecast errors of surface parameters are reduced up to the 18-h or 24-h forecast range. In the mid and in the upper troposphere, upper-level fields are also improved up to the 48-h forecast range when compared to radiosondes. Integrated Water Vapour comparisons indicate a positive benefit for at least 24 hours. Precipitation forecasts are found to be improved with the second re-analysis for a thresholds up to 10 mm/24-h. For higher thresholds, the frequency bias is degraded. Finally, improvement brought by the second re-analysis is illustrated with the Intensive Observation Period (IOP 8) associated with heavy precipitation over Eastern Spain and South of France.

H Okamura - One of the best experts on this subject based on the ideXlab platform.