C12G has created a new howto to explain the way to use OpenNebula with qcow images. Using them has the benefit of occupying less space, faster cloning time and solving problems related with sparse images. It is also a nice example on how OpenNebula behavior can be changed to suit the system administrator or infrastructure needs, in these case the storage model. There are still unexplored qcow feature besides the ones described in the text but it serves as the basis to implement them.