A volume translation apparatus and method are provided. The volume translation
apparatus resides between host machines and the physical storage devices accessed
by the host machines. This volume translation apparatus may perform volume translation
for the control path and optionally the data path of input/output (I/O) requests
sent by the host machines to the physical storage devices. Control path translation
ensures that the correct physical volumes are mounted for accessing by the I/O
request. Because the physical volume may be different from that requested by the
host machine application, the translation device includes a mapping that represents
which physical volumes represent copies of the virtual volume used by the host
machine application. When an I/O request is received and is directed to a particular
original virtual volume, the volume mapping apparatus translates the original virtual
volume identification into one or more physical volume identifications associated
with a secondary virtual volume which may or may not be the same as the original
virtual volume.