A storage apparatus and method are provided. The storage apparatus including includes a basic storage device having a control unit and an add-on storage device configured to be connected to the basic storage device. The add-on storage device including a first request receiving unit receiving a first operation stop request output from the basic storage device to the add-on storage device second request receiving unit receiving a second operation stop request different from the first operation stop request, communication monitoring unit monitoring communication from the basic storage device, and operation stop processing unit performing processing for stopping the operation of the add-on storage device. The operation stop processing unit determines the validity of the second operation stop request on the basis of a monitoring result obtained by the communication monitoring unit, and stops the operation of the add-on storage device.