Useable isn't just a myth.
Disclaimer: EMC Customer
The problem with "usable" capacity is every workload is different. When we do RMAN dumps to our XtremIo we only get about 2:1 at best as it's already compressed. When we run our oracle DB's we get more of a 3-4:1 compression rate. So I don't think there is a meaningful way to test a compression/duplication workload. Maybe someone can come up with a testbed?
I know our EMC rep has been bantering about some patent case Pure lost to EMC. (Were about to buy a new array) I wonder if that has anything to do with the missing reduction ticker??