I sthere a documented order of operations for upgrading from vCloud 1.5+ VCO Appliance + vSphere 5 to the vCloud 5.1 Suite?
I would like to minimize downtime of all components including vco workflows.
I am working on a document on how to upgrade from vCD 1.5 workflows to 5.1.
vCloud Director 1.5 to 5.1 workflow compatibility guide is the document I have put together. It has a lot of content based on my experience migrating custom workflows from 1.5 to 5.1 and from the people who wrote the plug-in. Now I may not cover the steps I would suggest to uprade a production environment.
On the prod side there are best practices for upgrading vSphere / vCloud. I would start with the official guides for vCloud upgrade here : http://www.vmware.com/support/pubs/vcd_pubs.html
If you have the option not to upgrade vCO during vSphere upgrade you should do it (I always install vCO on a separate VM for this purpose). Otherwise it si not a big deal since vCO 5.1 still works with the 1.5 plug-in and the workflows you wrote. Do not upgrade the 1.5 plug-in to 5.1 !
Once you get to the point where vCD / vSphere is upgraded to 5.1
I would test the vCO 4.X Server (or 5.1 if it was upgraded) + vCD 1.5 plug-in + unchanged workflows against vCD 5.1.
If everything work as expected you can stop there without doing any extra work.
If you have a mixed environment of orchestrated vCD 1.5 & 5.1 you must stop there since the 5.1 plug-in does not work with 1.5.
If you want to take advantage of the new 5.1 API and make your workflow use the new library items available in the 5.1 plug-in you need the following extra test / rework.
To port the workflows to 5.1 I would setup a test environment with a vanilla vCloud Suite 5.1 (you need at least vSphere 5.1, vCD 5.1, vCO 5.1). It can be based on the vCenter Server & vCenter Orchestrator 5.1 integration tips document
The first step would be to import the custom workflows as a package, validate them, update them if necessary as described in the vCloud Director 1.5 to 5.1 workflow compatibility guide until they are fully tested.
One important point is to make sure these do not use any workflows / actions from the 1.5 library that are not in the 5.1 one (you can either filter these out when importing the package and replacing them by their 5.1 counterpart, or import them, replace them and each time remove from package).
Then I would save this as a different package (see how I named them here).
To get these in production I would setup a new 5.1 server in which I would import the production workflows that have been ported and test them again against the production environment.
I would not perform a vCO 4.X + VCD 1.5 plug-in to vCO5.1 + vCD 5.1 plug-in because:
I hope this helps.