ESXi update package (zip, optional, will be used in Update Manager): update-from-esxi5.1-5.1_update01.zip;
SSO admin password;
vCenter service account password;
An account within local administrators group of vCenter server; and,
If you have Update Manager Client Plug-in installed on the same server of vCenter, it should be uninstalled before upgrading.
Phase 2: Upgrading vCenter and additions
Insert vCenter Installation disc or mount iso.
You cannot perform an upgrading installation by VMware vCenter Simple Install. It is required to upgrade all components manually as the same sequence as items listed in VMware vCenter Installer: vCenter Single Sign On, VMware vCenter Inventory Service, VMware vCenter Server, VMware vSphere Client (optional), VMware vSphere Web Client (optional) and VMware vSphere Update Manager.
While upgrading the SSO (vCenter Single Sign On), you will be notified to enter the SSO admin password. A restart is required after performing SSO upgrading.
Nothing more information is required while upgrading Inventory Service.
Password of vCenter service account is required while upgrading vCenter Server. It is possible but highly not recommended to change service address or port while upgrading.
All other 3 upgrading tasks are easy to perform. All you need is press Next button after starting the processes.
(Optional) Check the server status by logging on from vSphere Client.
(Optional) Install the Update Manager Client Plug-in now.
Phase 3: Upgrading ESXi
Log on vSphere Client with Update Manager Client Plug-in.
(Optional) Uploading ESXi upgrading package
In the Update Manager Tab of the top level of vCenter Hosts and Clusters (top item from the left panel), select Admin View.
In the Patch Repository tab, click Import Patches and upload update-from-esxi5.1-5.1_update01.zip. It will save downloading time of ESXi upgrading process.
Go back to Compliance View.
Scan your ESXi server.
(Optional) Stage. You may want to stage one server first to test your patch repository before staging all servers.
Remediate. You may need to set the servers in maintenance mode but not necessary. ESXi servers will be rebooted automatically after remediation.
Phase 4: VMtool upgrading
Upgrade VMtool on each virtual machine.
Phase 5: vSphere Client upgrading
Upgrade vSphere Client on all installed computer.
Phase 6: Troubleshooting
If there are some templates in your vSphere, you may need to convert them to virtual machine to upgrading VMtool. If this function is grayed out, you can remove the related template from inventory and add them back.