Abstract: With the rapid growth of storage scale, the key issues in building massive storage systems are to reduce the total cost of ownership (TOC) and to improve system performance. In this paper, the design and implementation of a tiered storage system, called TH-TS (Tsinghua Tiered Storage), are presented. In TH-TS, we design an approach for migrating files efficiently in tiered storage system (CuteMig), which promotes the files based on their promotion costs and benefits with the incremental scanning technique to acquire files access information and adaptively demotes files based on the free space of a high-end storage tier to ensure that the high-end storage system will have free space. It eliminates file replacement before promotion, and when files are promoted, it reserves their replicas in the low-end storage system. This approach solves the shortcomings of the traditional on-demand promotions and replacement demotion approaches, resulting in improved system performance and less amount of migrated data. The evaluation results reveal that TH-TS could effectively migrate files among different tiers, and reduce the average response time by 10% compared with LRU, and 39% compared with GreedyDualSize, and that TH-TS could reduce the amount of promoted data by 32% and 59%, and the amount of demoted data is also reduced by 47% and 66% compared with LRU and GreedyDualSize.