A storage device includes a nonvolatile memory device including a plurality of nonvolatile memories; a controller configured to allocate write blocks of the nonvolatile memory device to a plurality of streams provided from an outside; and a buffer memory configured to store a result of allocation of the write blocks to the plurality of streams, wherein the controller is further configured to reallocate the write blocks of the nonvolatile memory device to the plurality of streams based on the result of allocation stored in the buffer memory.