Patent ID: 8412869

Claim:
A computer system comprising: a host entity for issuing an input/output (I/O) request; a redundant storage virtualization controller (SVC) set coupled to the host entity for performing an I/O operation in response to the I/O request, in which the redundant SVC set comprises a first SVC and a second SVC, and the first SVC and the second SVC communicate with each other via a local bus; a physical storage device set coupled to the first SVC and the second SVC for providing the computer system with storage space; and a mechanism in the redundant SVC set for determining which SVC of the redundant SVC set is in an upstream mode and for determining which SVC of the redundant SVC set is in a downstream mode; wherein the second SVC takes over the first SVC automatically upon an abnormality occurring in the first SVC; and wherein a connection between the first SVC and the second SVC is established after one of the first SVC and the second SVC is in the upstream mode and after the other of the first SVC and the second SVC is in the downstream mode.