This has been known for well over a decade:  <i>volumes that use NTFS compression deliver performance increases as high as 50 percent over their uncompressed counterparts, depending on the type of data stored on the volumes</i><p><a href="http://technet.microsoft.com/en-us/library/cc767961.aspx" rel="nofollow">http://technet.microsoft.com/en-us/library/cc767961.aspx</a>