1. A method for extending N data node devices included in a distributed storage system, which further includes a server, wherein the server stores a hash ring of data nodes organized according to a distributed hash table (DHT), wherein the hash ring includes a plurality of partitions, and wherein each partition is mapped to a data node, the method performed by the server comprising: receiving an instruction of adding X new data nodes into the distributed storage system, wherein X is not less than 1; obtaining M of the partitions included in the hash ring; determining that M/(N+X) is lower than a preset threshold; generating new partitions by multiplying and mapping partitions to each data node, based upon the determination; storing mapping relationship between the new partitions and the X new data nodes; and adding the X new data nodes into the distributed storage system.