Before revision: In this paper, we investigate the effect ] of the prolonged service time at the non-dedicated servers in a pooling systemon the system performance. We consider the two-server loss model with exponential interarrival and service times. We show that if the ratio of the mean service time at the dedicated server and the mean prolonged service time at the non-dedicated server exceeds a certain threshold, pooling would become unfavourable. In particular, the threshold is explicitly provided. Moreover, when the degree of the prolonged service time is pre-specified, we show that the pooling system with prolonged service time at non-dedicated servers is not preferred when the work load in the systemis greater than a certain threshold .
After revision: In this paper, we investigate the effect ] of the prolonged service time at the non-dedicated servers in an asymmetric system. We study the independent system, the full flexibility system and the partial flexibility system when the occupation rate of the system, the degree of the prolonged service time is pre-specified, we show that the pooling system with prolonged service time at non-dedicated servers is not preferred when the work load in the systemis greater than a certain threshold .