Patent ID: 8868814

Claim:
An I/O system comprising: a plurality of single root-compatible PCI Express devices; a plurality of root complexes which share the plurality of PCI Express devices; a plurality of upstream PCI Express bridges connected to the plurality of root complexes, respectively; a plurality of downstream PCI Express bridges connected to the plurality of PCI Express devices, respectively; and a network through which data is exchanged between the plurality of upstream PCI Express bridges and the plurality of downstream PCI Express bridges, wherein each of the plurality of downstream PCI Express bridges comprises: a device control unit which performs a setting of each PCI Express device connected to each of the plurality of downstream PCI Express bridges itself before a BIOS is started-up on central processing units connected to the root complexes; a physical link control and monitoring unit which controls and monitors a state of a physical link with each PCI Express device connected to each of the plurality of downstream PCI Express bridges itself; and an error monitoring processing unit which performs monitoring and notification of an error of each PCI Express device connected to each of the plurality of downstream PCI Express bridges itself, wherein the plurality of upstream PCI Express bridges, the plurality of downstream PCI Express bridges, and the network constitute a virtual multi-root PCI Express switch.