To solve the "I/O wall" problem in the case of real-time accessing about mass information processing and to improve performance of distributed mass storage systems, an access policy based on storage unit pass-through is proposed and the problem of traditional access models is analyzed. Then the mechanism of pass-through pattern is studied, and a multi-level and distributed model is built up. Next, the continuous mapping of physical address, cache address of storage space and logical space address of storage system are realized depend on the different levels and mapping strategies. The time consuming of pass-through storage path in pass-through pattern is analyzed. Last, the performance of the storage unit in the simulated environment is tested. The results show that the method can improve the performance of storage system effectively, and can meet the needs of real-time accessing about massive information processing.