Patent ID: 8037362

Claim:
A method for use in a storage system for detecting the occurrence of a power failure, wherein the storage system includes: a base enclosure that includes: a first controller portion; a second controller portion; and an expansion enclosure that includes: a first switch; a second switch; one or more storage devices that are connected to the first switch and the second switch; and a power source that supplies power to the first switch, the second switch, and the one or more storage devices; a first group of links, including one or more links that connect the first controller portion and the first switch; and a second group of links, including one or more links that connect the second controller portion and the second switch; wherein the method comprises: the first controller portion transmitting a command targeted to a storage device from the one or more storage devices via each link in the first group of links; if transmission has failed for each command transmitted by the first controller portion via the links in the first group of links, the second controller portion transmitting a command targeted to a storage device from the one or more storage devices via each link in the second group of links; if transmission has failed for each command transmitted by the second controller portion via the links in the second group of links, the first controller portion transmitting a command targeted a storage device from the one or more storage devices via one of the links in the first group of links; if transmission has failed for the command transmitted by the first controller portion via the one of the links in the first group of links, the second controller portion transmitting a command targeted to a storage device from the one or more storage devices via one of the links in the second group of links; and if transmission has failed for the command transmitted by the second controller portion via the one of the links in the second group of links, the first controller portion determining that a power source failure has occurred in the expansion enclosure.