Recently, PCM (phase change memory) emerges as a new storage media and there is a bright prospect that PCM will be used as a storage device in the near future. Since the optimistic access time of PCM is expected to be almost identical to that of DRAM, we can make a question that the traditional buffer cache will be still effective for high speed secondary storage such as PCM. This paper answers it by showing that the buffer cache is still effective in such environments due to the software overhead and the bimodal block reference characteristics. Based on this observation, we present a new buffer cache management scheme appropriately for the system where the speed gap between the cache and storage is small. To this end, we analyze the condition that caching gains and find the characteristics of I/O traces that can be exploited in managing buffer cache for PCM-storage.