Device controller and input/output system

Abstract

An input/output request sent from a host is once cued through a channel adapter and is then transferred to a resource manager and is cued, and the cuing is distributed. Even if sequential input/output requests of the host are separated through a distribution processing to a plurality of paths, they are recognized on the device controller side and a countermeasure is taken. In the case in which a path from the host to the device controller is caused to be redundant into an operation system and a standby system, a path confirmation command is issued to the device drivers of a standby system path in order to confirm that the standby system path is normally operated or not. When the issuance of the input/output request is transferred to another path, a command for releasing the reserve of a transfer path is issued from another path. In the case in which one path of a device driver of an operation system causes a fault, switching to the use of the path of the device driver of the standby system is carried out to implement a load balance through the same processing distribution driver as that obtained before the generation of the fault. Even if a difference in a channel transfer rate is made between the host and the device controller, a higher transfer rate can be maintained.