to have two different master servers, one for each datacenter. Not only will you see better backup performance, having two master servers will provide you a level of redundancy you wouldnt have with just one. If you deploy one, then if it goes down you lose backups for both DC's. If you deploy both, obviously you've got a chance to at least back up half of your infrastructure.
For the second question, someone else should answer, as we have not yet moved to 7.