Sensitivity analysis of reliability and performability measures for a multi-server queueing system with constant retrial rate

The paper deals with the sensitivity analysis of reliability and performance measures for a multi-server queueing system where customers at the head of the queue retries to occupy a server in exponentially distributed time. The servers can differ in service and reliability characteristics. We have proved the insensitivity of the mean number of customers in the system to the type of allocation policy for equal service rates and confirmed a weak sensitivity in a general case of unequal service rates. A further sensitivity analysis is conducted to investigate the effect of changes in system parameters on a reliability function, a distribution of the number of failures of a server and a maximum queue length during a life time. © 2017, Springer International Publishing AG