Reliability of the two-unit priority standby system revisited

This paper deals with reliability assessment of the repairable two-unit cold standby system when the first, main unit has the better performance level than the second one. Therefore, after its repair, the main unit is always switched into operation. The new Laplace transform representation for the system’s lifetime is obtained for arbitrary operation and repair time distributions of the units. For some particular cases, the Laplace transform of the system is shown to be rational, which enables the use of the matrix-exponential distributions for obtaining relevant reliability indices. The discrete setup of the model is also considered through the corresponding matrix-geometric distributions, which are the discrete analogs of the matrix-exponential distributions.

Reliability Simulation of Two Component Warm-Standby System with Repair, Switching, and Back-Switching Failures under Three Aging Assumptions

We analyze the influence of repair on a two-component warm-standby system with switching and back-switching failures. The repair of the primary component follows a minimal process, i.e., it experiences full aging during the repair. The backup component operates only while the primary component is being repaired, but it can also fail in standby, in which case there will be no repair for the backup component (as there is no indication of the failure). Four types of system failures are investigated: both components fail to operate in a different order or one of two types of switching failures occur. The reliability behavior of the system is investigated under three different aging assumptions for the backup component during warm-standby: full aging, no aging, and partial aging. Four failure and repair distributions determine the reliability behavior of the system. We analyzed two cases—in the First Case, we utilized constant failure rate distributions. In the Second Case, we applied the more realistic time-dependent failure rates. We used three methods to identify the reliability characteristics of the system: analytical, numerical, and simulational. The analytical approach is limited and only viable for constant failure rate distributions i.e., the First Case. The numerical method integrates simultaneous Algebraic Differential Equations. It produces a solution in the First Case under any type of aging, and in the Second Case but only under the assumption of full aging in warm-standby. On the other hand, the developed simulation algorithms produce solutions for any set of distributions (i.e., the First Case and the Second Case) under any of the three aging assumptions for the backup component in standby. The simulation solution is quantitively verified by comparison with the other two methods, and qualitatively verified by comparing the solutions under the three aging assumptions. It is numerically proven that the full aging and no aging solutions could serve as bounds of the partial aging case even when the precise mechanism of partial aging is unknown.

Stochastic Analysis of a Priority Standby System under Preventive Maintenance

In this paper, we propose a system of two dissimilar units: one unit prioritizes operation (priority unit), and the other unit is kept as a cold standby (ordinary unit). In this system, we assume that the failures, repairs, and preventive maintenance (PM) times follow arbitrary distributions for both units, except for the fact that the repair time of the ordinary unit follows an exponential distribution. The priority unit has normal, partial failure or total failure modes, while the ordinary unit has normal or total failure modes. The PM of the system can be started after time t when (i) the priority unit is in the normal or partial failure modes up to time t and (ii) the standby unit is available up to time t. PM can be achieved in two types: the costlier type with probability p and the cheaper type with probability (1−p). Under these assumptions, we investigate the reliability measures of the system using the regenerative point technique. Finally, we show a numerical example to illustrate the theoretical findings and show the effect of preventive maintenance in the reliability measures of the proposed system.

PerformanceAnalysisof a StandbySystemusing Exponential-Rayleigh-Weibull Distributions

All through the life-cycle of a standby system, it is verychallenging to keep a standby unit workable.It may be fatalif the standby found non-workablewhen needed.This paper evaluates the performance of a standby systemworking under two primary constraintsby underlining the condition of the spare unit in standby mode. The first constraint is the maximum redundancy time for the standby and the second is maximum operation time for the operating unit.The standby unit failson exceeding the maximum time threshold andthereafterthe decision about its repair/replacement is subjected tothe inspection. While after surpassing the maximum operating time limit preventive maintenance is carried outfor the operating unit.To study the long-run performance or life-cycle of the system various performance indices have been analyzed usingthe theory of discrete-state continuous-time semi-Markov regenerative processes.Exponential, Rayleigh and Weibull probability distributions are used to study the system performance numerically.

Disaster Recovery Centre Menggunakan Hot Standby System pada BPR Universal

Kehidupan manusia pada saat ini tak bisa dilepaskan dari perkembangan teknologi informasi (TI), dimana manusia sudah sangat tergantung kepadanya. Bukan hanya individu manusia namun juga perusahaan, instansi pemerintah, institusi pendidikan pun juga sangat tergantung pada teknologi informasi. Pemanfaatan TI untuk kegiatan usaha keuangan, khususnya perbankan, sudah merupakan keharusan, baik operasional maupun layanan masyarakat dan promosi. Kegiatan bisnis BPR Universal yang mengandalkan TI sebagai sarana untuk meningkatan keuntungan dan kinerja tentulah menuntut tingkat ketersediaan sistem yang tinggi. Sistem dengan availabilitas tinggi sangat penting dimiliki, oleh karena itu diperlukan sebuah perencanaan untuk mengatasi masalah jika terjadi gangguan pada infrastruktur TI, server, aplikasi dan data. Untuk mengatasi masalah yang timbul setiap saat dan akan menimbulkan down time yang lama pada sistem data centre, maka diperlukan sebuah disaster recovery centre. Banyak cara atau metode yang dapat digunakan, namun pada tulisan ini akan dibahas penggunaan metode Hot standby untuk menanggulangi kegagalan sistem akibat bencana. Metode Sistem hot standby mengaktifkan semua infrastruktur TI data centre utama dan data centre cadangan, sehingga ketika terjadi masalah secara otomatis data centre cadangan akan langsung aktif untuk mengganti peran dari data centre utama dalam operasional.