Are you sure about these figures ? the difference seems too large. It's 

almost

unbelievable.

--

You should not, 
Mark Ruijter found the same for LessFS (http://www.lessfs.com/wordpress/?
p=688) and there is also such finding into an Hadoop thread 
(https://scribe.twitter.com/#!/otisg/status/148848850914902016)