In this paper, we propose to study the performance of a multi-server queuing system in which a customer requires simultaneous service from a random number of servers with the queuing disciplines retrial and preemptive priority. The infinitesimal generator matrix is presented for the proposed model and steady state measures are discussed. In particular, analytical expressions are obtained for the case where a customer (single type) requires simultaneous service from a random number of servers. Also, the generalised stochastic Petri net (GSPN) is developed for the proposed model and the particular cases. The performance of the models is analysed and compared, in terms of average system size and throughput. It is found that queuing systems in which a customer requires simultaneous service from a random number of servers performs better when the queuing discipline of retrial is appended into the system.