Upgrading is a multistage process in which procedures must be performed in a particular order. Follow the process outlined in this high-level overview to ensure a smooth upgrade with a minimum of system downtime.
Make sure that you understand the entire upgrade process before you attempt to upgrade. If you do not follow the safeguards, you might lose data and access to your servers. Without planning, you might incur more downtime than is necessary.
If you use vCenter Server Heartbeat in your vSphere deployment, use the vSphere Server Heartbeat installation and upgrade documentation to upgrade vCenter Server.
vCenter Server 5.5 removes support for Windows Server 2003 as a host operating system. See the VMware Compatibility Guide at http://www.vmware.com/resources/compatibility/search.php and Migrate vCenter Server and Components from a Windows Server 2003 Host.
vCenter Server 5.5 removes support for Windows Server 2008 SP1 as a host operating system. Upgrade Windows Server 2008 SP1 hosts to SP2 before upgrading vCenter Server to version 5.5. See the VMware Compatibility Guide at http://www.vmware.com/resources/compatibility/search.php and the Microsoft Software Lifecycle Policy at http://support.microsoft.com/lifecycle/#ServicePackSupport.
You must complete the upgrade process in a specific order because you can lose data and server access. Order is also important within each upgrade stage.
You can perform the upgrade process for each component in only one direction. For example, after you upgrade to vCenter Server 5.x, you cannot revert to vCenter Server 4.x. With backups and planning, you can restore your original software records.
You must complete one procedure before you move to the next procedure. Follow the directions within each procedure regarding the required sequence of minor substeps.
Because certain commands can simultaneously upgrade more than one stage, VMware recommends that you understand the irreversible changes at each stage before you upgrade your production environments.
To ensure that your datacenter upgrade goes smoothly, you can use vCenter Update Manager to manage the process for you.
vSphere upgrades proceed in the following sequence of tasks.
If your vSphere system includes VMware solutions or plug-ins, make sure they are compatible with the vCenter Server version that you are upgrading to. See the VMware Product Interoperability Matrix at http://www.vmware.com/resources/compatibility/sim/interop_matrix.php.
If you are upgrading vSphere components that are part of a VMware View environment, see Upgrading vSphere Components Separately in a Horizon View Environment.
Make sure your system meets vSphere hardware and software requirements.
See System Requirements.
Upgrade vCenter Single Sign-On, vCenter Inventory Service, vCenter Server, and the vSphere Web Client.Important:
If you use vCenter Server Heartbeat in your vSphere deployment, use the vSphere Server Heartbeatinstallation and upgrade documentation to upgrade vCenter Server and related components.
See Upgrading vCenter Server. Use the topic Required Information for Installing or Upgrading vCenter Single Sign-On, Inventory Service, vCenter Server, and the vSphere Web Client to create a worksheet with the information you will need when you install vCenter Single Sign-On, vCenter Inventory Service, and vCenter Server.
If you use VMware Update Manager, upgrade VMware Update Manager.
Upgrade your ESXi hosts.
See Upgrading and Migrating Your Hosts. vSphere provides several ways to upgrade hosts:
Use vSphere Update Manager to perform an orchestrated upgrade of your ESXi hosts. See Using vSphere Update Manager to Perform Orchestrated Host Upgrades.
Upgrade a single host at a time, interactively, from an ESXi ISO installer image stored on a CD, DVD, or USB flash drive. See Upgrade or Migrate Hosts Interactively.
Use a script to perform an unattended upgrade for multiple hosts. See Installing, Upgrading, or Migrating Hosts Using a Script
If a host was deployed using vSphere Auto Deploy, you can use Auto Deploy to upgrade the host by reprovisioning it. See Using vSphere Auto Deploy to Reprovision Hosts.
Upgrade or patch ESXi 5.x hosts by using esxcli commands. See Upgrading Hosts by Using esxcli Commands.
Reapply your host license.
Upgrade virtual machines and virtual appliances, manually or by using VMware Update Manager to perform an orchestrated upgrade.