Abstract: A disk array data storage system has plural sets of storage disks connected to multiple corresponding I/O buses. Individual storage disks can be independently and asynchronously attached to or detached from corresponding interfacing slots of the I/O buses. The system has physical device drivers which represent the storage disks with respect to their connections to the interfacing slots of the I/O buses and physical device managers which represent the data kept on the storage disks. Interface drivers are provided to manage I/O transfers through corresponding I/O buses. When a particular storage disk is attached to or detached from an interfacing slot of an I/O bus, the interface driver corresponding to the I/O bus freezes all I/O requests that come from the physical device drivers that represent the storage disks in the set connected to the I/O bus. A configuration manager determines which interfacing slot the particular storage disk has been attached to or detached from.