The present invention is storage apparatus where {HEAD ~ an intermediary device} is arranged between a controller and {TAIL ~ a plurality} of disk devices of different performances arranged in a hierarchical manner 
is arranged between
The present invention is storage apparatus where { HEAD ~ an intermediary device } is arranged between a controller and { TAIL ~ a plurality } of disk devices of different performances arranged in a hierarchical manner
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH