A method for issuing a partition balancing subtask, applied to a controller, wherein the controller and at least two nodes form a storage system, each node comprises at least one partition, wherein a node fault triggers a partition balancing task, and the method comprises: generating, by the controller, a first partition balancing task, after a first node is faulty to recover the partitions on the first node; calculating, by the controller, a first target partition distribution information, wherein the first target partition distribution information is partition distribution information that needs to be formed; generating, by the controller, a first partition balancing subtask set on a basis of the first partition balancing task, according to migration partitions, source nodes of the migration partitions, and destination nodes of the migration partitions, wherein the first partition balancing subtask set is a set of partition balancing subtasks that need to be executed for partition distribution information of the storage system to change from a current partition distribution information to the first target partition distribution information; wherein a partition balancing subtask records a migration partition, and a source node and a destination node of the migration partition, wherein the migration partition is a copy of the partition on a faulty node and is located on another node; sending, each partition balancing subtask in the first partition balancing subtask set, to the destination node of each partition balancing subtask to execute data migration; generating a second partition balancing subtask set after a second partition balancing task is received, wherein the second partition balancing subtask set comprises at least one partition balancing subtask, and each partition balancing subtask records: a migration partition, a node to which the migration partition belongs, and a destination node; searching a current partition balancing subtask set, and deleting a repeated partition balancing subtask between the second partition balancing subtask set and the current partition balancing subtask set, wherein the current partition balancing subtask set comprises partition balancing subtasks being executed in a first partition balancing subtask set; and issuing each partition balancing subtask in the second partition balancing subtask set to the destination node of each partition balancing subtask to execute data migration, after the repeated partition balancing subtask is deleted to the destination node recorded in each partition balancing subtask. generating, by the controller, a first partition balancing task, after a first node is faulty to recover the partitions on the first node; calculating, by the controller, a first target partition distribution information, wherein the first target partition distribution information is partition distribution information that needs to be formed; generating, by the controller, a first partition balancing subtask set on a basis of the first partition balancing task, according to migration partitions, source nodes of the migration partitions, and destination nodes of the migration partitions, wherein the first partition balancing subtask set is a set of partition balancing subtasks that need to be executed for partition distribution information of the storage system to change from a current partition distribution information to the first target partition distribution information; wherein a partition balancing subtask records a migration partition, and a source node and a destination node of the migration partition, wherein the migration partition is a copy of the partition on a faulty node and is located on another node; sending, each partition balancing subtask in the first partition balancing subtask set, to the destination node of each partition balancing subtask to execute data migration; generating a second partition balancing subtask set after a second partition balancing task is received, wherein the second partition balancing subtask set comprises at least one partition balancing subtask, and each partition balancing subtask records: a migration partition, a node to which the migration partition belongs, and a destination node; searching a current partition balancing subtask set, and deleting a repeated partition balancing subtask between the second partition balancing subtask set and the current partition balancing subtask set, wherein the current partition balancing subtask set comprises partition balancing subtasks being executed in a first partition balancing subtask set; and issuing each partition balancing subtask in the second partition balancing subtask set to the destination node of each partition balancing subtask to execute data migration, after the repeated partition balancing subtask is deleted to the destination node recorded in each partition balancing subtask.