[Rdo-list] Upgrade from Icehouse to Juno on Centos 6.5

Hello We have an relatively big OpenStack setup (> 150 Compute Nodes) based on CentOS 6.5 with the RDO Icehouse release. We now considering an upgrade to Juno, is there a best practice out there how to do it and how is it with the depending CentOS upgrade to 6.6 or even 7.0? Any help is appreciated! Thanks, Chris