ReFS

ReFS: The next generation file system

http://hyper-v-backup.unitrends.com/refs-generation-file-system-part-1/

http://hyper-v-backup.unitrends.com/refs-generation-file-system-part-2/

http://blogs.msdn.com/b/b8/archive/2012/01/16/building-the-next-generation-file-system-for-windows-refs.aspx