Notes on vCenter upgrade from 4.0 to 4.1

This upgrade initiative is basically because it is found that Storage I/O Control is not available on ESX 4.0.  It is available on ESX 4.1 or later only.  However, vCenter 4.0 is not compatible with ESX 4.0 with the errors below.

Adding a ESX/ESXi 4.1 host to vCenter Server 4.0 fails with the error: interal error:vmodl.fault.hostCommunication

Notes about the vCenter upgrade from 4.0 to 4.1

1. The Guided Consolidation 4.0 extension has to be uninstalled before the vCenter upgrade.

2. The Update Manager 4.0 needs to be upgraded to 4.1 after the vCenter upgrade

3. The vCenter upgrade takes approximate 15 minutes for my installation with 2 ESX hosts.  The upgrade time largely depend on the size of the database

4. During the upgrade, the connection to vCenter will be disconnected but the current Virtual Machines and ESX hosts are still up and running

5. Make sure the account details to start up the vCenter Web Services are entered correctly or else the Web Services might fail to start up after the upgrade