The SmartTier option is built on multi-volume support technology. Using SmartTier, you can map more than one volume to a single file system. You can then configure policies that automatically relocate files from one volume to another, or relocate files by running file relocation commands. Having multiple volumes lets you determine where files are located, which can improve performance for applications that access specific types of files. SmartTier functionality is a separately licensed feature.
See About SmartTier.