A Stochastic Reward Nets Model for Time based Software Rejuvenation in Virtualized Environment

Modern business has a 24x7 non-stop running and the availability of the business continuity for everything, from everywhere, at all time is a growing requirement. System outages are more often due to software fault, than hardware fault. Software availability is one of the weakest links in system availability. Several studies have reported that one of the causes of unplanned software outages is the software aging phenomenon. Server virtualization is becoming so reliable and cost effective solutions for the availability of the business continuity. In virtualization environments, the hypervisor or virtual machine monitor (VMM) itself or virtual machines (VM) can fail with software failure. Software rejuvenation is one of the promising techniques assuring high availability of server virtualized system. To prevent system failures caused by software aging in both VM and VMM, software rejuvenation can be applied. The work presented in this paper aims to offer high availability against software aging of virtualized server system by providing both VM clustering software rejuvenation and VM migration based software rejuvenation analytic model using stochastic reward nets (SRN) for time based rejuvenation policy. Numerical examples are presented to illustrate the applicability of the model. The numerical derivation results are validated with the evaluation results through SHARPE tool.