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Kishor S. Trivedi - One of the best experts on this subject based on the ideXlab platform.
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optimization of two granularity software Rejuvenation policy based on the markov regenerative process
IEEE Transactions on Reliability, 2016Co-Authors: Gaorong Ning, Rivalino Matias, Javier Alonso, Jing Zhao, Kishor S. TrivediAbstract:Software Rejuvenation is a proactive software control technique that is used to improve a computing system performance when it suffers from software aging. In this paper, a two-granularity inspection-based software Rejuvenation policy, which works as a closed-loop control technique, is proposed. This policy mitigates the negative impact of two-level software aging. The two levels considered are the user-level applications and the operating system. A Markov regenerative process model is constructed based on the system condition. We obtain the degradation rate of the application software and operating system from fault injection experiments. The diagnostic accuracy of the adopted monitor and analysis system, which is applied to inspect the application software and operating system, is considered as we provide the optimal Rejuvenation strategies. Finally, the availability and the overall loss probability with their corresponding optimal inspection time intervals are obtained numerically based on the parameter values estimated from the experiments. Experimental results show that two-granularity software Rejuvenation is much more effective than traditional single-level software Rejuvenation. In our experi-mental study, when two-granularity software Rejuvenation is used, the unavailability and the overall loss probability of the system were reduced by 17.9% and 2.65%, respectively, in comparison with the single-level Rejuvenation.
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modeling and analysis of software Rejuvenation in a server virtualized system with live vm migration
Performance Evaluation, 2013Co-Authors: Fumio Machida, Kishor S. Trivedi, Dong Seong Kim, Fumio Machida, Dong Seong Kim, Kishor S. TrivediAbstract:As server virtualization is used in a number of IT systems, the unavailability of virtual machines (VM) on server virtualized systems becomes a significant concern. Software Rejuvenation is a promising technique for improving the availability of server virtualized systems as it can postpone or prevent failures caused by software aging in both the VM and the underlying virtual machine monitor (VMM). In this paper, we study the effectiveness of a combination of VMM Rejuvenation and live VM migration. When a VMM needs to be rejuvenated, the hosted VMs running on the VMM can be moved to another host using live VM migration and continue the execution even during the VMM Rejuvenation. We call this technique Migrate-VM Rejuvenation and construct an availability model in the stochastic reward net for evaluating it in comparison with the conventional approaches; Cold-VM Rejuvenation and Warm-VM Rejuvenation. The designed model enables us to find the optimum combinations of Rejuvenation trigger intervals that maximize the availability of VM. In terms of the maximum VM availability, Migrate-VM Rejuvenation is potentially the best approach. However, the advantage of Migrate-VM Rejuvenation depends on the type of live VM migration (stop-and-copy or pre-copy) and the policy for migration back to the original host after VMM Rejuvenation (return-back or stay-on). Through numerical examples, we show that ''pre-copy'' live VM migration is encouraged rather than pure ''stop-and-copy'' migration and it is better to return back VM to the original host soon after the VMM Rejuvenation (i.e., ''return-back'' rather than ''stay-on'' policy) for high-availability. The effect of the VMM Rejuvenation technique on the expected number of transactions lost is also studied by combining the availability model with an M/M/1/n queueing model.
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A comparative experimental study of software Rejuvenation overhead
Performance Evaluation, 2013Co-Authors: Javier Alonso, Rivalino Matias, Vicente, A. Maria, Kishor S. TrivediAbstract:In this paper we present a comparative experimental study of the main software Rejuvenation techniques developed so far to mitigate the software aging effects. We consider six different Rejuvenation techniques with different levels of granularity: (i) physical node reboot, (ii) virtual machine reboot, (iii) OS reboot, (iv) fast OS reboot, (v) standalone application restart, and (vi) application Rejuvenation by a hot standby server. We conduct a set of experiments injecting memory leaks at the application level. We evaluate the performance overhead introduced by software Rejuvenation in terms of throughput loss, failed requests, slow requests, and memory fragmentation overhead. We also analyze the selected Rejuvenation techniques' efficiency in mitigating the aging effects. Due to the growing adoption of virtualization technology, we also analyze the overhead of the Rejuvenation techniques in virtualized environments. The results show that the performance overheads introduced by the Rejuvenation techniques are related to the granularity level. We also capture different levels of memory fragmentation overhead induced by the virtualization demonstrating some drawbacks of using virtualization in comparison with non-virtualized Rejuvenation approaches. Finally, based on these research findings we present comprehensive guidelines to support decision making during the design of Rejuvenation scheduling algorithms, as well as in selecting the appropriate Rejuvenation mechanism.
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Modeling and analysis of software Rejuvenation in a server virtualized system
2010 IEEE Second International Workshop on Software Aging and Rejuvenation, 2010Co-Authors: Fumio Machida, Dong Seong Kim, Kishor S. TrivediAbstract:As server virtualization is used as an essential software infrastructure of various software services such as cloud computing, availability management of server virtualized system is becoming more significant. Although time-based software Rejuvenation is useful to postpone/prevent failures due to software aging in a server virtualized system, the Rejuvenation schedules for virtual machine (VM) and virtual machine monitor (VMM) need to be determined in a proper way for the VM availability, since VMM Rejuvenation affects VMs running on the VMM. This paper presents analytic models using stochastic reward nets for three time-based Rejuvenation techniques of VMM; (i) Cold-VM Rejuvenation in which all VMs are shut down before the VMM Rejuvenation, (ii) Warm-VM Rejuvenation in which all VMs are suspended before the VMM Rejuvenation and (iii) Migrate-VM Rejuvenation in which all VMs are moved to the other host server during the VMM Rejuvenation. We compare the three techniques in terms of steady-state availability and the number of transactions lost in a year. We find the optimal combination of Rejuvenation trigger intervals for each Rejuvenation technique by a gradient search method. The numerical analysis shows the interesting result that Warm-VM Rejuvenation does not always outperform Cold-VM Rejuvenation in terms of steady-state availability depending on Rejuvenation trigger intervals. Migrate-VM Rejuvenation is better than the other two as long as live VM migration rate is large enough and the other host server has a capacity to accept the migrated VM.
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Performability analysis of clustered systems with Rejuvenation under varying workload
Performance Evaluation, 2007Co-Authors: Dazhi Wang, Wei Xie, Kishor S. TrivediAbstract:This paper develops time-based Rejuvenation policies to improve the performability measures of a cluster system. Three Rejuvenation policies, namely standard Rejuvenation, delayed Rejuvenation and mixed Rejuvenation, are designed to improve the cluster's performability under varying workload. Analytic models are built to evaluate these three policies. Since deterministic transitions are used in this paper and analytical models based on homogeneous continuous-time Markov chains (CTMC) do not allow non-exponential distributions, we utilize deterministic and stochastic Petri nets (DSPN), in which the underlying stochastic process is a Markov regenerative process (MRGP), to capture both exponential and deterministic distributions. System performability measures under these three Rejuvenation policies are derived based on the DSPN models. We show that the mixed Rejuvenation policy achieves the maximum performability among the three policies, which results in 12% improvement on the system throughput in the example shown in this paper. The delayed Rejuvenation is better than the standard Rejuvenation with respect to the optimal job blocking probability and system throughput. For longer Rejuvenation-triggering intervals, the standard Rejuvenation yields a better result than delayed Rejuvenation, while for shorter Rejuvenation-triggering intervals the delayed Rejuvenation policy outperforms standard Rejuvenation policy.
Tadashi Dohi - One of the best experts on this subject based on the ideXlab platform.
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A transient interval reliability analysis for software Rejuvenation models with phase expansion
Software Quality Journal, 2019Co-Authors: Junjun Zheng, Hiroyuki Okamura, Tadashi DohiAbstract:The phenomenon of software aging refers to the continuing degradation of software system performance with the operation time and is usually caused by the aging-related bugs such as the memory leak and the accumulation of round-off errors. Software Rejuvenation acts as one of the proactive fault management techniques against the software aging. In this paper, we evaluate the interval reliability for two basic stochastic models with periodic software Rejuvenation by Garg et al. ( 1995 ) and Suzuki et al. ( 2002a , b ). The interval reliability is one of the most generalized dependability measures that involve commonly used reliability function and steady-state availability as the special cases, and is helpful for the system design during a fixed mission period. From the mathematical point of view, the interval reliability for the software Rejuvenation models leads to the transient analysis. We focus on the phase expansion approach for solving the transient solutions for the basic software Rejuvenation models. The phase expansion is an approximate technique that replaces arbitrary probability distributions by the phase-type (PH) distributions. Benefiting from the phase expansion, we can numerically derive the transient interval reliability for two software Rejuvenation models. In numerical examples, we discuss the accuracy of the phase expansion and also reveal quantitative properties of the interval reliability measures.
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Toward high assurance software systems with adaptive fault management
Software Quality Journal, 2014Co-Authors: Koichiro Rinsaka, Tadashi DohiAbstract:In this paper, we develop an adaptive approach to estimate the optimal preventive Rejuvenation schedule, which maximizes the steady-state system availability. We formulate the upper and lower bounds of the predictive system availability using the one-look ahead predictive survival function from system failure time data and derive the pessimistic and optimistic Rejuvenation policies. Then, we derive adaptive Rejuvenation policies from the original data together with a right-censored observation. In the simulation experiments, we show the usefulness of the adaptive nonparametric predictive inference approach proposed in this paper.
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ISSRE Workshops - Non-parametric predictive inference of adaptive software Rejuvenation schedule
2008 IEEE International Conference on Software Reliability Engineering Workshops (ISSRE Wksp), 2008Co-Authors: Koichiro Rinsaka, Tadashi DohiAbstract:In this paper we develop an adaptive approach to estimate the optimal preventive Rejuvenation schedule which maximizes the steady-state system availability. We formulate the upper and lower bounds of the predictive system availability using the one-look ahead predictive survival function from system failure time data, and derive the pessimistic and optimistic Rejuvenation policies. Then, we derive adaptive Rejuvenation policies from the original data together with a right-censored observation.
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Estimating Periodic Software Rejuvenation Schedules under Discrete-Time Operation Circumstance
IEICE Transactions on Information and Systems, 2008Co-Authors: Kazuki Iwamoto, Tadashi Dohi, Naoto KaioAbstract:Software Rejuvenation is a preventive and proactive solution that is particularly useful for counteracting the phenomenon of software aging. In this article, we consider periodic software Rejuvenation models based on the expected cost per unit time in the steady state under discrete-time operation circumstance. By applying the discrete renewal reward processes, we describe the stochastic behavior of a telecommunication billing application with a degradation mode, and determine the optimal periodic software Rejuvenation schedule minimizing the expected cost. Similar to the earlier work by the same authors, we develop a statistically non-parametric algorithm to estimate the optimal software Rejuvenation schedule, by applying the discrete total time on test concept. Numerical examples are presented to estimate the optimal software Rejuvenation schedules from the simulation data. We discuss the asymptotic behavior of estimators developed in this paper.
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estimating discrete time periodic software Rejuvenation schedules under cost effectiveness criterion
International Journal of Reliability Quality and Safety Engineering, 2006Co-Authors: Kazuki Iwamoto, Tadashi Dohi, Naoto KaioAbstract:Software Rejuvenation is a preventive and proactive solution that is particularly useful for counteracting the phenomenon of software aging. In this article, we consider the similar periodic software Rejuvenation model to Garg et al.13 under the different operation circumstance. That is, we model the stochastic behavior of telecommunication billing applications by using a discrete-time Markov regenerative process, and determine the optimal periodic software Rejuvenation schedule maximizing the so-called cost effectiveness, in discrete-time setting. Also, we provide a statistically non-parametric method to estimate the optimal software Rejuvenation schedule, based on the discrete total time on test concept. Numerical examples are devoted to illustrate the determination/estimation of the optimal software Rejuvenation schedule and to examine the asymptotic behavior of the estimator developed here.
Yehuda Ullmann - One of the best experts on this subject based on the ideXlab platform.
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intense pulsed light for skin Rejuvenation hair removal and vascular lesions a patient satisfaction study and review of the literature
Annals of Plastic Surgery, 2009Co-Authors: Lucian Fodor, Nurit Carmi, Adriana Fodor, Ytzhack Ramon, Yehuda UllmannAbstract:There are very few studies in the English literature that evaluate the patient satisfaction after treatment using intense pulsed light (IPL) and there is no reported study comparing the results of the three major IPL applications: Rejuvenation, hair removal, and treatment of small vascular lesions. This study was designed to compare results after IPL treatment for skin Rejuvenation, hair removal, and vascular lesions. Three groups of 30 consecutive patients having skin Rejuvenation, hair removal, and small vascular lesions were selected and treated with the same IPL system. The evaluation was performed 1 year after the last treatment for the following parameters: age, sex, skin type, satisfaction, willingness to continue the treatment, willingness to recommend the treatment, and complications. Most of the minor complications occurred in the Rejuvenation group (86.6%). No complications were recorded for 67% of patients having hair removal and for 75% having vascular lesion treatment. There was no significant difference in the level of satisfaction between the 3 groups (Kruskal Wallis test; P = 0.257). No difference regarding satisfaction was recorded in this study, but complications were more frequently encountered after Rejuvenation. The findings of this study are useful when discussing IPL treatments with patients considering IPL procedures.
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Using intense pulsed light for cosmetic purposes: our experience.
Plastic and Reconstructive Surgery, 2004Co-Authors: Lucian Fodor, Yaron Rissin, Anuska Gaiman, Liron Eldor, Oren Shoshani, Yitzchak Ramon, Isaac J. Peled, Yehuda UllmannAbstract:The authors’ experience using intense pulsed light for skin Rejuvenation is summarized and analyzed with regard to its efficacy, safety, and complications. Rejuvenation using intense pulsed light was performed on 59 patients over a 6-month period (January of 2002 to July of 2002); these patients ser
Junjun Zheng - One of the best experts on this subject based on the ideXlab platform.
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A transient interval reliability analysis for software Rejuvenation models with phase expansion
Software Quality Journal, 2019Co-Authors: Junjun Zheng, Hiroyuki Okamura, Tadashi DohiAbstract:The phenomenon of software aging refers to the continuing degradation of software system performance with the operation time and is usually caused by the aging-related bugs such as the memory leak and the accumulation of round-off errors. Software Rejuvenation acts as one of the proactive fault management techniques against the software aging. In this paper, we evaluate the interval reliability for two basic stochastic models with periodic software Rejuvenation by Garg et al. ( 1995 ) and Suzuki et al. ( 2002a , b ). The interval reliability is one of the most generalized dependability measures that involve commonly used reliability function and steady-state availability as the special cases, and is helpful for the system design during a fixed mission period. From the mathematical point of view, the interval reliability for the software Rejuvenation models leads to the transient analysis. We focus on the phase expansion approach for solving the transient solutions for the basic software Rejuvenation models. The phase expansion is an approximate technique that replaces arbitrary probability distributions by the phase-type (PH) distributions. Benefiting from the phase expansion, we can numerically derive the transient interval reliability for two software Rejuvenation models. In numerical examples, we discuss the accuracy of the phase expansion and also reveal quantitative properties of the interval reliability measures.
Maaloul Alia - One of the best experts on this subject based on the ideXlab platform.
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Optimised Migrate Virtual Machine Rejuvenation
Journal of Computational Chemistry, 2015Co-Authors: Sanheji Manel, Azizi Ridha, Maaloul AliaAbstract:Server virtualization is an essential component in virtualized software infrastructure such as cloud computing. Virtual machines are generated through a software called virtual machine monitor (VMM) running on physical servers. The risks of software aging caused by aging-related bugs affect both VM and VMM. As a result, service reliability degrades may generate huge financial losses to companies. This paper presents an analytic model using stochastic reward nets for timebased Rejuvenation techniques of VMM and VM. We propose to manipulate the VM behavior while the VMM Rejuvenation is according to the load on the system. Using a previous Petri net model of virtualized server, we performed an algorithm in order to optimize Rejuvenation technique and achieve high availability. So we perform Migrate-VM Rejuvenation or Warm-VM Rejuvenation while there are current jobs in the system. Although Migrate-VM Rejuvenation is better than Warm-VM Rejuvenation in steady state availability, it can’t be always performed as it depends on the capacity of the other host. When the queue is empty and the virtual machine has no current jobs to serve, we propose to combine both VMM Rejuvenation and VM Rejuvenation. We show that the proposed technique can enhance the availability of VMs.
