According to the vSphere 4.0 release notes (http://www.vmware.com/support/vsphere4/doc/vsp_esx40_vc40_rel_notes.html )
vCenter Server 4.0 becomes unresponsive in large environments if managing ESX Server 3.5 hosts prior to ESX 3.5 patch 10
vCenter Server 4.0 can become unresponsive in large environments after 30 days if it manages any ESX Server 3.5 hosts prior to ESX Server 3.5 patch 10.
Workaround: Upgrade to ESX Server 3.5 Update 4 if you are running ESX Server 3.5 with vCenter Server 4.0.
What exactly is “patch 10”? How do you know what build level qualifies? Is there a single patch that can be applied?
If you upgrade to vCenter 4 and things become unresponsive after 30 days, patching all your disparate ESX servers isn’t going to be something that most large organizations can do quickly. I’d say this is an important one.
I posed the question to my local SE, and several VMware contacts I have, but no-one seems to know. Can anyone out there on the tubes clarify this one?