As they wait for these virtualization industry growing pains to subside, Mercury and other companies continue to pine for a utility future. "For Mercury to consider storage a utility, we'd have to have an environment that is fully integrated between the operating system, the file system and the block level. That way, when an application needs more storage, the virtualized environment would automatically increase the resources and send a message back to the server," Kreisa says. "That's the endgame, and it's still a ways out."

from: http://www.networkworld.com/supp/2008/ndc3/051908-storage-virtualization... is the conclusion of a good article on what "Utility storage" the main product that 3PAR sells.