Of all the upgrades I have done to date, this was by far the easiest. Perhaps it was practice or even VMware vSphere’s time in market, but the upgrade to vSphere ESXi 5.1 from v4.1 and v5.0 went flawlessly. Here are the steps I took:
When I upgraded vCenter to v5.1, I made sure to upgrade VMware Update Manager as well. Into this new Update Manager I imported the ESXi image from the 5.1.0a ISO I downloaded. With this I was ready to perform my upgrades. I have 4 nodes to upgrade and as such I started with the node sitting at ESXi v4.1, which had been powered off for almost a year now. As part of this upgrade process I also purchased more licensing to cover this node. It is time to retire v4.1 and move to the future.
Import ESXi v5.1.0a ISO into VMware Update Manager (VUM)
Added ESXi 5.1.0a to the baseline I use in VUM
Select the ESXi 5.1.0a baseline element for my v4.1 node and pressed Remediate
Now I have a shiny new ESXi 5.1.0a system that I brought into my existing vCenter Cluster of ESXi hosts. Now I can begin updating all the other hosts in a rolling manner, one at a time so that VMs can be automatically migrated to other nodes, with a few exceptions. The major exception to this is VMware vCenter Operations (vCops), which needs to be moved by hand. Every time I try to have this automatically moved, it fails to move, as the CDROM drives must be connected for normal operation.
Steps per node:
Check VM list to determine if vCops is on the node, if so vMotion the vCops component or components to a previous updated node.
Using VUM for the specific node, select the baseline element and Upgrade.
Wash, rinse, repeat until all nodes are upgraded.
Since I also have HP hardware I want to upload to each node the HP Offline bundle so that HP Insight Manager can gain a better view of the environment. This is considered an extension by VUM but you use the Import Patches mechanism to pull the offline bundle into VUM.