A data processing method and system and a client, where a target storage node is determined in a manner of comparing a second vector of received data and first vectors that are corresponding to all storage nodes and prestored on the client that receives the data, and the target storage node no longer needs to be determined in a manner of extracting some fingerprint values as samples from received data and sending the fingerprint values to all storage nodes in a data processing system for query, and waiting for a feedback from the storage nodes.