Frank wrote:
But you wrote that the hosts are not on the HCL. If this Cluster is your production environment and you have support on that, i would not recomend to update. Because when you come into trouble with something related to vmware and your hosts are not on the hcl, i am not sure what happend with your call.
he means, they are not on the HCL for vSphere 5, but they are for vSphere 4.1.
it is supported to have a vCenter 5.1 with vSphere 4.1