A storage system, wherein the storage system comprises a controller and a solid state disk, the controller is capable of communicating with the solid state disk, the solid state disk comprises multiple channels, and each of the multiple channels is connected to multiple dies, wherein the controller is configured to: create multiple segments; select a first die from the multiple dies; select a first segment from the multiple segments, and determine an available offset of the first segment; generate a write request, wherein the write request comprises a write address, target data, and a data length of the target data, and the write address comprises an identifier of a channel connected to the first die, an identifier of the first die, an identifier of the first segment, and the available offset; and send the write request to the solid state disk; the solid state disk is configured to receive the write request, and store the target data according to the write address and the data length of the target data; and wherein the controller is further configured to record an amount of valid data stored in each of the multiple dies; and the controller is specifically configured to select a die in which an amount of valid data is less than a second threshold as the first die; wherein selecting the first die based on the second threshold comprises - valid data amount balancing principle, wherein if there are multiple dies in which the amounts of valid data are less than the second threshold, the controller has a processing manner: selecting a die in which an amount of valid data is smallest as the first die. the controller is configured to: create multiple segments; select a first die from the multiple dies; select a first segment from the multiple segments, and determine an available offset of the first segment; generate a write request, wherein the write request comprises a write address, target data, and a data length of the target data, and the write address comprises an identifier of a channel connected to the first die, an identifier of the first die, an identifier of the first segment, and the available offset; and send the write request to the solid state disk; the solid state disk is configured to receive the write request, and store the target data according to the write address and the data length of the target data; and wherein the controller is further configured to record an amount of valid data stored in each of the multiple dies; and the controller is specifically configured to select a die in which an amount of valid data is less than a second threshold as the first die; wherein selecting the first die based on the second threshold comprises - valid data amount balancing principle, wherein if there are multiple dies in which the amounts of valid data are less than the second threshold, the controller has a processing manner: selecting a die in which an amount of valid data is smallest as the first die. - valid data amount balancing principle, wherein if there are multiple dies in which the amounts of valid data are less than the second threshold, the controller has a processing manner: selecting a die in which an amount of valid data is smallest as the first die.