Gluster users - May 2018 - Upgrade OS on Server node

All,

I have a Distributed-Replicate volume served by 10 servers (Number of 
Bricks: 5 x 2 = 10). They are currently running CentOS 6 and I want to 
upgrade them to CentOS 7.

I know there are several ways I could go about it, but I was wondering 
if there is a best-practice that alleviates down/rebuild time.

All the best,

Brian Andrus