In data storage research, optimization of storage system performance and usability is a common hot topic. iSCSI storage system has advantages like big capacity, high performance and good expansibility, but the problem of the lag between disk I/O speed and processor speed, disk I/O speed and net transmission speed still can't be solved. In order to solve the bottleneck of disk reading and writing in SAN, this article puts forward a method to reduce the delay by creating virtual disk on different server memory in network storage cluster. The experiment result shows this method increases net storage system performance effectively.