I have to echo the sentiments of a few people here. You can't compare WHSv1 or WHSv2 to RAID, I mean really. It was never intended to "replace" that in terms of efficient redundancy. However, for those of us who are or are planning (as I am) to use RAID the additional 12% overhead of simply using WHSv2 WITHOUT duplication is an actual fair consideration/comparison when looking at say Server 2008 R2 with some shares against WHSv2 without duplication.