There is disclosed a RAID control apparatus which copies data to a copying-target disk drive from the first or second disk drive by use of a rebuilding function in a disk array system including the first and second disk drives. A placement is generated for timing critical logic associated with each included embedded memory in a logic design. The filler tube has a bottom portion and a top portion. 5 nm or more and 1 nm or less is obtained, followed by a finishing process such that the average surface roughness of said surface becomes 0. A line switch control device provides for closing only of the line switches on those local data lines which belong to the segment in which a write or read mode takes place. Alternatively, backoff may be made for each or multiple clusters or even individually for each respective cluster.