The embodiment of the invention discloses a data writing-in method, system and device. According to the technical scheme, when clients write data into files of a data storage server, it is guaranteed that only one client writes the data into the files by carrying the sequence number corresponding to the files allocated to the clients in a mode that the clients race to control the sequence number, and therefore safety of the data is guaranteed. Compared with an existing lease management mechanism, loads of the server is reduced, performance of the system is improved, higher response speed can be achieved, and recovery time delay is very short.