an apparatus for use in a storage device having at least two clusters , each including a disk control device having a plurality of channel controllers that send and receive commands and data to and from an upper system , a plurality of disk controllers that control disk units , and a cache that temporarily stores data between the upper system and the disk units . the apparatus includes a first bus included in a first cluster . the first bus is connected to the channel controller , the disk controller and the cache of the first cluster . a second bus is included in a second cluster . the second bus is connected to the channel controller , the disk controller and the cache of the second cluster . a common resource is connected to the first bus of the first cluster and the second bus of the second cluster . the common resource includes a specified set of data which is commonly accessible from each of the channel controllers or the disk controllers of the clusters .