A large RAID system may consist of several PCI bus segments since a PCI bus segment can connect only a limited number of disks. In this paver, PCI bus transactions in a RAID system are classified in terms of the initiator and the target of the transaction. Also, the data transfer time of each transaction type is analyzed. By using the analysis results, read and write performance of two RAID system configurations are formulated. From simulation of the RAID system using the DEVS formalism, performance of the configurations are evaluated and compared with the analytical results while changing various system parameters.