In a distributed storage system, a method for extending a number N of data node devices comprises a server receives an instruction of adding X new data nodes into the distributed storage system. Then, the server obtains a number M of the all partitions included in a hash ring and determines that M/(N+X) is lower than a preset threshold. The hash ring is organized according to a distributed hash table (DHT), and includes a plurality of partitions. Each partition is mapping to a data node. Based upon the determination, the server generates new partitions by multiplying partitions mapping to each data node, based upon the determination. After storing mapping relationship between the new partitions and the X new data nodes, the server adds the X new data nodes into the distributed storage system.