A data storage device may include: a nonvolatile memory; and a controller configured to control an operation of the nonvolatile memory. When a command is received from a host, the controller transfers first state information as a response to the command to the host, the first state information including first time information indicating time difference from when the command is received to when a task corresponding to the command is generated and stored. When a task execution command is received from the host, the controller transfers second state information as a response to the task execution command to the host, the second state information including second time information indicating time difference from when the task execution command is received to when the task is completed.