you might want also to consider to build a backup free storage like the centera. We have a Product called "EVnearSync" where you can excactly recieve this benefit with "any" kind of storage.
Archived Data is statical, so a reliable second copy should be enough for a DR scenario.
Btw. RPO (Recovery Point Obective) - the allowed Dataloss- is "0" and RTO (Recovery Point Objective) - the Time the System is online again with all Data - is less than 15 minutes.
Have a look on "http://www.evtools.net/products/ev-nearsync"