Low Description
The current behaviour of snapshot repair is to let one node at a time calculate a merkle tree. This is to ensure only one node at a time is doing the expensive calculation. The drawback is that it takes even longer time to do the merkle tree calculation.
In a multi-DC setup, I think it would make more sense to have one node in each DC calculate the merkle tree at the same time. This would yield a significant improvement when you have many data centers.
I'm not sure how relevant this is in 2.1, but I don't see us upgrading to 2.1 any time soon. Unless there is an obvious drawback that I'm missing, I'd like to implement this in the 2.0 branch.