If you use VMware Update Manager (VUM), you can use VUM to upgrade your ESX servers to vSphere 4.0u1. The best way to do this depends on your VMware license. If you have vMotion and DRS you can put one ESX host in your cluster in maintenance mode. All the VM's will be automatically moved to other hosts in your cluster. You can then remediate the host in maintenance mode. After the first host is upgraded, you can upgrade the other hosts the same way.
Regards, Robert
Blog: https://rvdnieuwendijk.com/ | Twitter: @rvdnieuwendijk | Author of: https://www.packtpub.com/virtualization-and-cloud/learning-powercli-second-edition
