Memory storage technologies, such as next generation non-volatile (NV) memory and battery backed NV-DIMM, are emerging. While they provide much higher performance than the current block storage devices, such as SSDs and HDDs, their capacities are limited. Such limitation makes it difficult to adapt memory storage for mass storage; thus, its uses have been limited. This paper proposes a method that combines block storage with memory storage and makes use of memory storage as cache of block storage. The proposed method effectively utilizes the high performance of memory storage and also provides the large capacity of block storage. Therefore, memory storage can be transparently used as a part of mass storage while its low overhead access can accelerate storage performance. The proposed method was implemented as a device driver of the Linux kernel. Its performance evaluation shows that it outperforms a bare SSD drive and a drive that combines memory storage and a SSD by the existing method.