Improving the performance and usability of storage systems has been a popular subject in data storage research. Memory, disks and networks are the three most important components in a network storage system. However, the development of these three is unbalanced. Improvements in memory technology will double memory capacity within 18 months according to Moore?s Law. The network transfer speed is growing fast too. But advances in disk performance have been slow. Aiming at this problem, this paper proposes a method to create virtual disks the memory of various servers on network storage clusters. Furthermore, a high performance and platform-compatible memory disk - SAN-MDS (SAN Memory Disk System) is presented. Experimental results show that SAN-MDS can effectively improve the network storage systems? performance in executing write (especially synchronous write) operations and decrease write latency.