When ever you need to migrate to from one vCenter instance to another there are lots of things you need to migrate.
This PowerCLI script will help you migrate members from one DRS VM group to another. It can easily be modified to be part of a bigger context, or migrate all groups available.
The prerequisites are that you have both the new and the old vCenter running, and that you have disconnected you hosts in the old vCenter and connected them to the new one. Do NOT remove them from you old vCenter. Leave them disconnected.
Back in the day it was customary to divide your VMs into three “blue” folders. I was not uncommon to see the three folders named High Priority, Normal Priority and Low Priority, and then people would distribute the VMs into those folders. The reason they were called blue folder was because it was really resource pools created in a DRS cluster in the Hosts and Clusters view in vCenter. And they were not made to logically divide you VMs into “folders”.
The problem with this approach is that unless you regularly reconfigured these resource pools you would get unexpected performance. I was not uncommon for an installation to have 5-10% of the VMs in the high priority “folder”, 80% in the normal priority “folder” and 5-10% in the low priority “folder”. The problem with this is that if you then select High, Normal and Low shares for these folders, you will not get the performance you would expect.