As you are moving to a VXRail im not sure your be able to upgrade the older vCenter. I maybe wrong but i've deployed a few VXRails and they always come with their own VXRail manager and vCenter and new hosts already attached.
You can then add this to the Connection servers as a new vCenter, use the VM migration fling to move Images over and update Pools. As you use Composer you will need to spin off a new server for this as it doesn't run with the virtual appliance (1 Composer at a time).
Ive been talking things over with Dell and they said there is no issue using the vCenter we already have for the vXrail as long as its 6.7.
But they werent able to give me much insight on the migration tool.
Ide be worried if we used a new vCenter then i would have issues with all my pool and entitlements Dont want to have to recreate them by moving to a new vCenter.
Eventually when we bring in the new vXrail we will need to migrate the master images and create new pools and entitlements but we can do it slowly.
Anyone have experience using the vcenter migration tool with a VDI env?
Are you also decomissioning the original 6.0 hosts after the VxRail migration is done? You can have either the internal VCSA or external VCSA (external is BYO) - VxRail will support either.
It would be much less risky and easier to just have both environments side-by-side. The beauty is that Horizon supports multiple vCenters, so you can easily just add your new vCenter, build new pools, and start migrating users over.
Now would also be a good time to switch to Instant Clones with your new pools, and get off your linked clones. If you don't have Horizon Enterprise, you can upgrade to Horizon 8 first, which includes Instant Clones in all licensing. Linked clones are now deprecated in Horizon 8.
I wouldn't worry about pools & entitlments as that is managed by the connection servers. As you will use the same hostname/ip of the current vCenter that shouldn't cause you mush of an issue. Assuming you are going with the self signed cert you will need to "re trust" it in the Horizon admin page under servers(This is normal for self signed)
Spin off a new Composer server before you even start the upgrade and let that settle for a few day then make sure you snapshot the vCenter once you are ready, pause all provisioning and start.