Reply to Message

First I would install a new 5.0 vCenter as 5.0 can manage both the 4.x ESX/i hosts and the new 5.0 hosts.

     Install vComposer 2.7 on vCenter 5.0

Next I would take one or two of my current 4.x hosts and remove them from the cluster.  Hopefully your cluster can handle at least 2 host failures (if it can handle 3 then take two out of service).  Upgrade those hosts to 5.0.

Form a new 5.0 cluster with these hosts.  Make sure the hosts have access to all the datastores they need.

Setup a new 5.0 View Connection Server.  Point it to your 5.0 vCenter.

Copy/Import/Clone/Whatever your original Master Image to the new cluster, update its Hardware and Vmware Tools.  OR  Build a new clean Master VM.  Hopefully you have solid documentation on the exact process you go through to create the Master Image (and all updates).  If this is the case, I normally use a View refresh as an opportunities to start a clean Master Image.

Update the Agent on the Master Image.

Use the View Admin on the new VCS to create a pool using the updated Master Image.  (Pick a pool that isn't huge and if possible is full of users that will give you good feedback).

On the client side, change the VCS URL for those clients that are going to use this pool.  You can do this using Group Policy so they don't even realize you've done anything.

Continue this process.  As you free up space on the old system continue to remove ESX hosts and add them to the new system.

Before you know it everyone gets migrated over and they shouldn't even be aware.

And the best part, if you screw up at any point in time, just point them back to the orginal VCS URL and they can go back to the pool they are currently using.  THIS is why I like this type of migration, there is a great punt stratigy.  I'm all about CYA when doing something this important.  A straight upgrade doesn't CYA as well as a swing.

Gunnar