We evaluate the performance of the copy network under three scenarios: (1) non-buffer non-splitting copy network (NBNS), (2) shared-input buffer-non-splitting copy network (SIBNS), and (3) shared-input-buffer-splitting copy network (SIBS). For NBNS, we derived the exact overflow and cell loss probabilities instead of the Chernoff bound. Furthermore, we propose a general Markov model, a novel theoretical approach, for the performance analysis of the shared-input-buffer copy networks. This analysis method can be applied for both SIBNS and SIBS. In our work, theoretical and simulation results are presented for every scenario. The comparison shows that improved performance of lower cell loss and higher throughput can be achieved by shared-input-buffer (SIBNS and SIBS). However the tradeoff is the long cell delay. With the splitting algorithm, SIBS can provide better performance than the NBNS and SIBNS.