I'm currently running a few ESX 3.0.1 servers alongside VC 2.0.1. I'm planning to upgrade the ESX servers to 3.5, but not for a couple of months.
I understand you need to upgrade VC to 2.5 as a prerequisite to the ESX upgrade which is good as I'd like to take a look at the new features in VC2.5, i.e. update manager and guided consolidation.
1. Are there any known issus with running VC2.5 alongside 3.0.1 servers?
2. To take advantage of using update manager and guided consolidation, do the ESX servers themselves have to be updated and are there any associated issues?
1. I had no issues running VC 2.5 with any of the older versions of ESX. I have a mixed environment where my 2.5 VC is managing ESX 2.5x, 3.02, and 3.5 hosts.
2. One horrible experience I have upgrading my VC is migrating the database over to the environment. If you made the same mistake as me of using the default local database for DB then you will have to recreate the DB. There is no way for VC 2.5 to import the local database. This was really a pain point when you have over 40 ESX hosts and a ton of permissions linked to the VC.
If you have a small enivornment then this is not a big deal you just have add everything back to the new VC.
1. There have been some issues regarding the vc agent not installing properly, and causing a few headaches to uninstall and re-install. Other than that, after the agent issues have been resolved, the hosts work just fine with 2.5. I updated one of my environments over a month back, and have not had issues.
2. Update manager only works for ESX 3.5 hosts, so it won't work to patch 3.0.x servers. You will have to upgrade or re-install 3.5 to make it work with Update Manager. Guided consolidation works just fine, and you don't need anything special to use it other than the vc 2.5 server itself.