Markovian availability modeling for software‐intensive systems

It is important to take into account the trade‐off between hardware and software systems when total computer‐system reliability/performance is evaluated and assessed. Develops an availability model for a hardware‐software system. The system treated here consists of one hardware and one software subsystem. For the software subsystem, in particular, it is supposed that: the restoration actions are not always performed perfectly; the restoration times for later software failures become longer; and reliability growth occurs in the perfect restoration action. The hardware‐ and software‐failure occurrence phenomena are described by a constant and a geometrically decreasing hazard rate, respectively. The time‐dependent behavior of the system is described by a Markov process. Useful expressions for several quantitative measures of system performance are derived from this model. Finally, numerical examples are presented for illustration of system availability measurement and assessment.