hierarchical storage management
n.
A mass storage device that automatically moves data from expensive, rapid-access online media to less-expensive, nearline storage based on the frequency of use of the data.
Notes
Hierarchical storage management systems generally keep frequently used data on high-speed hard drives. As the frequency of access decreases, typically with age, data may be moved to compressed formats on hard drives, then to optical disks, and ultimately to tape. Moving data to slower media saves significantly on storage costs.
