Automated tiered storage
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Automated tiered storage (also automated storage tiering) is the automated progression or demotion of data across different tiers (types) of storage devices and media. The movement of data takes place in an automated way with the help of a software and is assigned to the related media according to performance and capacity requirements. Here, the intelligence is driven by a software and so Automated Tiered Storage can be tagged as a characteristic of a Software Defined Storage.
Data progression examples from DataCore Software and Dell Compellent
A software based example of automated tiering which can work across SSDs, Flash Memory devices, different types of storage devices and arrays and Cloud storage is available from DataCore and is a feature of their storage hypervisor software. Other examples can be found in this 'comparison article on auto tiered storage'.
An example of automated tiered storage in a hardware storage array is a feature called Data Progression from Compellent Technologies. Data Progression has the capability to transparently move blocks of data between different drive types and RAID groups such as RAID 10 and RAID 5. The blocks are part of the "same virtual volume even as they span different RAID groups and drive types. Compellent can do this because they keep metadata about every block -- which allows them to keep track of each block and its associations."
Automated Tiered Storage as used by Apple in fall 2012 iMac as Fusion Drive
Fusion Drive combines the high storage capacity of a traditional hard drive with the high performance of flash storage. Disk-intensive tasks — from booting up to launching apps to importing photos — are faster and more efficient because frequently used items are kept at the ready on speedy flash storage, while infrequently accessed items go to the hard drive. 
In a caching solution files live on the hard disk drive and are temporarily mirrored to the SSD cache as needed. In an enterprise auto-tiering situation, and with Fusion Drive, the data is moved from one tier to another, rather than only being temporarily cached there." 
- Russ Taddiken – Senior Storage Architect (2006). Automating Data Movement Between Storage Tiers. Retrieved from the UW Records Management Web site: http://www.compellent.com/
- Tony Asaro, Computerworld. "Compellent-Intelligent Tiered Storage." January 19, 2009.
- "Apple iMac Performance Website" October 24, 2012.
- "Apple Fusion Drive—wait, what? How does this work?" October 24, 2012.