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In Pictures: 10 excellent new features in Windows ...
Closely related to Storage Tiering is the ability to pin selected files to a specific tier. Pinning makes it possible to ensure that files you always want on the fastest storage, such as boot disks in a Virtual Desktop Infrastructure deployment, will never be moved to the slower storage tier. Otherwise, files that you always want to take advantage of SSDs might be moved to the HDD tier after some period of relative inactivity.
In Pictures: 10 excellent new features in Windows Server 2012 R2