The ever growing storage demands of modern applications cultivate a promising area of storage system management, centered upon metadata servers. Some of the works are done at the file system level, which care little about device level data organization. In this paper we present the design of managing metadata at block-level by using storage virtualization techniques. We propose both static and dynamic block mapping policies to meet the diverse needs of applications, balance disk workload and improve storage system performance. We build our prototype in a Virtual Interface based storage area network, and the evaluation results demonstrate that metadata management at block-level can be efficient and flexible.