This might be the single most exciting new feature in Windows Server 2012 R2. In essence, Storage Tiering is the ability to dynamically move chunks of stored data between different classes of storage, such as fast SSDs and slower hard drives. Many high-end storage systems have had automated tiering for years, but this is the first time you are able to do it at the operating system level. Microsoft uses a heat-map algorithm to determine which chunks of data are seeing the most activity and automatically moves the "hottest" chunks to the fastest tier. You can adjust the settings for how and when the data is moved using PowerShell.