Storage Tiering, the practice of moving frequently accessed data to very fast storage, while maintaining infrequently accessed data on moderate or slow storage is supported with Storage Spaces starting in Windows Server 2012 R2. Frequency of access (heat) on files is measured by the file system and fed into a tiering engine that instructs Spaces to move often used files to flash-based storage devices, while retaining cold data on large-capacity, slow storage. The major benefit is a significant increase in cost efficiency, as only the critical workload is accelerated by the flash-based storage, yet the majority of data stored can remain on slow, large-capacity devices (for example, 7,200 RPM 4TB HDDs). 



To learn more about Storage Tiering, as well as sizing recommendations, please refer to the following TechEd content:

1. Best Practices for Deploying Tiered Storage Spaces in Windows Server 2012 R2

    (http://channel9.msdn.com/Events/TechEd/NorthAmerica/2014/DCIM-B346#fbid  =)

2. Delivering Exceptional IOPS/$ with Windows Server 2012 R2 

    (http://channel9.msdn.com/events/TechEd/NorthAmerica/2014/DCIM-B311#fbid  =)


Ref:http://social.technet.microsoft.com/wiki/contents/articles/15200.storage-spaces-designing-for-performance.aspx