• STOCHASTIC MODELLING OF A CLOUD WITH INDEPENDENT H/W AND S/W FAILURE SUBJECT TO MAXIMUM OPERATION AND REPAIR TIMES

Abstract

The present paper focuses on some reliability and economic measures of a cloud having independent h/w and s/w failure. For this purpose, a stochastic model is developed considering cloud as a single unit. A server is provided to do PM, repair and replacement of the components upon their failures immediately. After a maximum operation time the unit undergoes for preventive maintenance directly from normal mode. If repair of the component is not possible up to a pre-specific time (called Maximum Repair Time), the components are replaced by new one with some replacement time. However, only up-gradation of the software components by new one is made after failures. The failure time of the components follow negative exponential distribution while the distributions of preventive maintenance, repair,  up-gradation and replacement times are taken as arbitrary with different probability density functions. Various reliability indices are obtained using semi-Markov process and regenerative point technique. Graphs are drawn for a particular case to depict the behaviour of MTSF, availability and profit function.