A redundant external storage virtualization computer system. The redundant
storage virtualization computer system includes a host entity for issuing
an IO request, a redundant external storage virtualization controller
pair coupled to the host entity for performing an IO operation in
response to the IO request issued by the host entity, and a plurality of
physical storage devices for providing storage to the computer system.
Each of the physical storage devices is coupled to the redundant storage
virtualization controller pair through a point-to-point serial signal
interconnect. The redundant storage virtualization controller pair
includes a first and a second storage virtualization controller both
coupled to the host entity. In the redundant storage virtualization
controller pair, when the second storage virtualization controller is not
on line, the first storage virtualization controller will take over the
functionality originally performed by the second storage virtualization
controller.