A storage client needs to store to-be-written data into a distributed storage system, and storage nodes corresponding to a first data unit assigned for the to-be-written data by a management server are only some nodes in a storage node group. When receiving a status of the first data unit returned by the management server, the storage client may determine quantities of data blocks and parity blocks needing to be generated during EC coding on the to-be-written data. The storage client stores the generated data blocks and parity blocks into some storage nodes designated by the management server in a partition where the first data unit is located. Accordingly, dynamic adjustment of an EC redundancy ratio is implemented, and the management server may exclude some nodes in the partition from a storage range of the to-be-written data based on a requirement, thereby reducing a data storage IO amount.