(1) The logical ordering of primary storage pools, based on the speed and capacity of the devices that the storage pools use, as defined by the appropriate administrator.
(2) An arrangement of storage devices with different speeds and capacities. The levels of the storage hierarchy include: main storage, such as memory and direct access storage device (DASD) cache; primary storage (DASD containing user-accessible data); migration level 1 (DASD containing data in a space-saving format); and migration level 2 (tape cartridges containing data in a space-saving format). See also hierarchical storage management, migration level 1, migration level 2, object storage hierarchy, primary storage.