Abstract

A computer system is analyzed considering the concept of priority to Preventive Maintenance (PM) over hardware repair subject to maximum operation and repair times. Two-identical units of the computer system have been taken up-one is initially operative and other is kept as spare in cold standby. In each unit, hardware (h/w) and software (s/w) work together and may fail independently from normal mode. There is a single server who visits the system immediately when needed to carry out repair activities. PM of the unit is conducted after a Maximum Operation Time (MOT). If repair of the h/w is not possible up to a maximum repair time, it is replaced by a new one with some replacement time. However, only replacement of the s/w is made giving some replacement time with the new one when s/w fails to execute the program properly. Priority to PM of the unit is given over h/w repair. The failure time of the unit follows negative exponential distribution while the distributions of PM, repair and replacements are taken as arbitrary. To carry out the cost-benefit analysis, expressions for several reliability measures are obtained by using semi-Markov and regenerative point technique. The graphical behaviour of some important performance measures of the system has been examined giving particular values to various parameters and costs.

Highlights

  • In spite of increasing development and availability of new computer technologies, little work has been dedicated to the ­cost-­benefit analysis of the computer systems with independent failure of h/w and s/w components

  • It is a matter of record that, not much work related to the reliability modeling of computer systems with the concepts of Preventive Maintenance (PM), Maximum Operation Time (MOT) and Maximum Repair Time (MRT) has been reported so far in the literature

  • Time to System Failure (MTSF), availability and profit are drawn with respect to Preventive Maintenance rate (B) for fixed values of other parameters including a 0.7 and b 0.3 as shown respectively in Figures 2, 3 and 4

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Summary

Introduction

In spite of increasing development and availability of new computer technologies, little work has been dedicated to the ­cost-­benefit analysis of the computer systems with independent failure of h/w and s/w components. It is a matter of record that, not much work related to the reliability modeling of computer systems with the concepts of PM, MOT and Maximum Repair Time (MRT) has been reported so far in the literature. The expressions for various reliability measures such as Mean Time to System Failure (MTSF), availability, busy period of the server due to Preventive Maintenance, repair, hardware replacement, software replacement, expected number of software replacements, hardware replacements and expected number of visits of the server are derived by using ­semi-­Markov process and regenerative point. 4228 Cost-Benefit Analysis of a Computer System with Priority to Preventive Maintenance over Hardware Repair f(t) / F(t) : pdf/cdf of the time for PM of the unit qij(t)/Qij(t) : pdf / cdf of passage time from regenerative state i to a regenerative state j or to a failed state j without visiting any other regenerative state in

Transition Probabilities and Mean Sojourn Times
Steady State Availability
Busy Period Analysis for Server
Expected Number of Replacements of the Units
Conclusion
10. Acknowledgement
11. References
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