A storage system includes first and second expanders for connecting storage units, each of the first and second expanders being connected cascade each other, a first controller connected one of the first and one of the second expanders and a host, a second controller connected the one of the second expanders, the one of the first expanders and the host, the second controller detecting a failure of at least one of the first controller, the first expanders and the second expanders, the second controller selectively controlling a first boot sequence which boots the first controller after the first expanders have been booted and a second boot sequence which boots the first controller before the first expanders have been booted, determining one of the first boot sequence and the second boot sequence on the basis of a place where a failure has occurred in a recovery process.