So the upgrade process for vCenter is actually pretty simple, you simply use the vCenter installer you used to initially install vCenter and simply select upgrade instead. Essentially what is happening during this process is a new VCSA is being created with a different IP and all of the configuration, hosts, and settings are being moved to the VCSA at the upgraded version and once it’s the done the original IP is assigned to the VCSA and operation continues normally. A few things I will note is when upgrading vCenter or any other appliance it is important to make sure everything is compatible with each other. I would recommend reviewing update release notes or https://interopmatrix.vmware.com/Interoperability. When performing vCenter upgrades it is best to follow this procedure, Backup configuration, snapshots, offline backups, etc. Then, update the vCenter server to your target version. Next, update your ESXi hosts, I will get more into that in a moment. Finally update your VMs, hardware version, VMware tools, etc. In order to update the ESXi hosts you will need to utilize the vSphere Life Cycle Manager. You can locate this tool under the life cycle management tab in vCenter. You will need to find the iso of the ESXi version you are wishing to upgrade to and upload that to your VLCM. From there you create a baseline under the baseline tab in VLCM with this ISO, which I discussed previously in my host profiles post, this baseline is what is used to upgrade your ESXi hosts, after it is created you can assign the baseline to the clusters/hosts you would like to upgrade under Inventory > Cluster > Update > Baseline > Attach. Once you have the ESXi iso for your target version in the VLCM, and the baseline created and assigned to your cluster you can go to the cluster in inventory you would like to upgrade, select the updates tab and check compliance on the cluster. It is important to check compliance since vCenter may not detect the hosts as out of compliance and ready for remediation until doing so. Once compliance is checked you should receive the option under Cluster > Update > Baseline to remediate when selecting the ESXi baseline created before, once you click remediate vCenter will go through each host and update. Once it is done you can check compliance again under update and the cluster should be compliant confirming upgrade was successful. As always please feel free to leave comments on this post! I may take a short break from these posts due to encroaching holidays but will do my best to stay active on this site.