Automated Storage Tiering (AST)
Automated storage tiering (AST) is a storage software management feature that dynamically moves information between different disk types and RAID levels to meet space, performance and cost requirements.
Automated storage tiering features use policies that are set up by storage administrators. For example, a data storage administrator can assign infrequently used data to slower, less-expensive SATA storage but allow it to be automatically moved to higher-performing SAS or solid-state drives (SSDs) as it becomes more active (and vice versa).
The technology, pioneered by Compellent Technologies in its Storage Center Data Progression product in 2005 (Compellent has since been acquired by Dell Inc.), automatically classifies and migrates data to the optimum tier of storage.
Sub-LUN automated storage tiering moves data at a more granular level.