Method for switching node and an information processing system

An information processing system configured to control execution enablement/disablement of I/O requests from plural host computers to a disk device, comprising:

• each of said host computers including:
• an I/O request unit for issuing an I/O request to which said I/O request unit has added host identification information for identifying said respective host computers, and
• an access-right change command unit for transmitting an access-right change command to said disk device, said access-right change command including one piece or plural pieces of information having I/O-enable/disable information and said host identification information correspond to each other in a one-to-one correspondence manner, said I/O-enable/disable information indicating whether or not said disk device will execute said I/O requests from said host computers;
• and
• said disk device including:
• an access-right management table for storing and holding said access-right change commands from said host computers,
• an access control unit for identifying request-source host computers of said I/O requests, and for judging whether to enable/disable said I/O requests to be executed on each host-computer basis, based upon said host identification information and said access-right management table, and
• an access-right change unit that, in accordance with said access-right change commands from said host computers within said access-right management table, changes in a batch of said I/O-enable/disable information on each host-computer basis,
• said disk device enabling or disabling said I/O requests on each host-computer's node basis, with said host computers being said I/O request sources.