When you upgrade or migrate a deployment with multiple vCenter Server instances, the upgrade or migration order matters.

You upgrade or migrate externally deployed vCenter Single Sign-On 5.5 instances or Platform Services Controller 6.0 instances first. You temporarily leave the vCenter Server instances at version 5.5 or version 6.0 while you complete the upgrade or migration process for the vCenter Single Sign-On 5.5 instances or Platform Services Controller 6.0 instances.

You must upgrade or migrate your vCenter Single Sign-On 5.5 instances or Platform Services Controller 6.0 instances sequentially.

For a mixed-platform installation with vCenter Single Sign-On 5.5 instances or Platform Services Controller 6.0 instances on Windows and vCenter Server Appliance instances, upgrade or migrate all the vCenter Single Sign-On 5.5 instances or Platform Services Controller 6.0 instances on Windows before upgrading any vCenter Server Appliance instances.

For a mixed-platform installation with vCenter Single Sign-On 5.5 appliances or Platform Services Controller 6.0 appliances and vCenter Server instances on Windows, upgrade all the vCenter Single Sign-On 5.5 appliances or Platform Services Controller 6.0 appliances before upgrading or migrating any vCenter Server instances on Windows.

After upgrading or migrating your vCenter Single Sign-On 5.5 instances or Platform Services Controller 6.0 instances, you can upgrade vCenter Server instances. vCenter Server instances that point to the same Platform Services Controller can be upgraded or migrated concurrently.

When you upgrade an externally deployed vCenter Single Sign-On 5.5 instance or Platform Services Controller 6.0 instance to an externally deployed Platform Services Controller 6.5 instance, the legacy vCenter Server instances that were using the component are not affected. The legacy vCenter Server instances continue to operate with the upgraded Platform Services Controller just as they operated before the upgrade without any problems or required reconfiguration. Legacy vCenter Server instances continue to be visible to the legacy vSphere Web Client, though vCenter Server 6.5 instances are not visible to the legacy vSphere Web Clients.

Transitional behavior during a migration from a vCenter Server deployment on Windows to an appliance deployment is the same as for a vCenter Server upgrade on Windows.

Mixed-version transitional behavior is the same for vCenter Single Sign-On instances deployed in vCenter Server 5.5 for Windows environments and in vCenter Server Appliance environments.

Mixed-Version 5.5 and 6.5 Transitional Environment
vCenter Server deployment with Platform Services Controller 6.5 instance, vCenter Server 5.5 instance, and vCenter Server 6.5 instance

Important

Mixed-version environments are not supported for production. Use these environments only during the period when an environment is in transition between vCenter Server versions.

If you upgrade an external vCenter Single Sign-On 5.5 and at least one instance of vCenter Server to version 6.5 while leaving other instances of vCenter Server at version 5.5, expect the following behavior:

Linked Mode no longer functions.

vCenter Server 5.5 instances continue to operate with the upgraded Platform Services Controller as they did before the upgrade without any problems or required reconfiguration.

In a mixed-version 5.5 and 6.5 environment, a vSphere Web Client 6.5 instance shows vCenter Server 5.5 instances.

vSphere Web Client 5.5 shows vCenter Server instances only, not 6.5 instances.

When you upgrade the external vCenter Single Sign-On 5.5 instance to an external Platform Services Controller 6.5 instance, and all vCenter Server 5.5 instances to version 6.5, none of the vCenter Server instances are affected. They continue operating with the Platform Services Controller as they did before the upgrade, without any problems or required action.

The transitional order and behavior are the same for vCenter Server 6.0 environments when upgrading or migrating to vCenter Server 6.5 environments. The vCenter Server 6.0 instances continue operating with the Platform Services Controller 6.5 instance as they did before the upgrade or migration, without any problems or required action.

The only action required for a mixed-version environment after transition is a restart of any legacy vSphere Web Client instances if they will be used to view vCenter Server instances that are not yet upgraded or migrated.

Example vSphere 5.5 Deployment Before Transition Begins
vCenter Server external deployment with two external vCenter Single Sign-On 5.5 instances and three vCenter Server 5.5 instances

Example vSphere 6.0 Deployment Before Transition Begins
vCenter Server external deployment with two external Platform Services Controller 6.0 instances and three vCenter Server 6.0 instances

For example, a deployment with three vCenter Server instances and two external vCenter Single Sign-On instances must be upgraded or migrated one instance at a time to version 6.5.

Example vSphere 5.5 Deployment in Transition at Step 1
vCenter Server external deployment with one external vCenter Single Sign-On 5.5 instance, one external Platform Services Controller 6.5 instance, and three vCenter Server 5.5 instances

Example vSphere 6.0 Deployment in Transition at Step 1
vCenter Server external deployment with one external Platform Services Controller 6.0 instance, one external Platform Services Controller 6.5 instance, and three vCenter Server 6.0 instances

Upgrading or migrating the first external vCenter Single Sign-On instance or Platform Services Controller instance to an external Platform Services Controller of the current version has no impact on the legacy vCenter Server instances except that Linked Mode no longer functions for version 5.5 instances.

Example vSphere 5.5 Deployment in Transition at Step 2
vCenter Server external deployment with two external Platform Services Controller 6.5 instances and three vCenter Server 5.5 instances

Example vSphere 6.0 Deployment in Transition at Step 2
vCenter Server external deployment with two external Platform Services Controller 6.5 instances and three vCenter Server 6.0 instances

Upgrading or migrating the second external vCenter Single Sign-On instance or Platform Services Controller instance to the current version has no impact on the behavior of the legacy vCenter Server instances.

Example vSphere 5.5 Deployment in Transition at Step 3
vCenter Server deployment with two external Platform Service Controller 6.5 instances, one vCenter Server 6.5 instance, and two vCenter Server 5.5 instances

Example vSphere 6.0 Deployment in Transition at Step 3
vCenter Server external deployment with two Platform Services Controller 6.5 instances, one vCenter Server 6.5 instance, and two vCenter 6.0 instances

After upgrading the first vCenter Server instance to 6.5, changes occur in the connectivity between the vCenter Server instances.

The two remaining legacy vSphere Web Client instances can no longer view the newly upgraded vCenter Server 6.5 instance after it joins the Platform Services Controller instance.

The legacy vSphere Web Client instances can still view the legacy vCenter Server instances after they are restarted.

The vSphere Web Client 6.5 instance that is part of the newly upgraded vCenter Server 6.5 instance can view the legacy vCenter Server instances and 6.5 instances.

Example vSphere 5.5 Deployment in Transition at Step 4
vCenter Server external deployment with two Platform Service Controller 6.5 instances, two vCenter Server 6.5 instances, and one vCenter Server 5.5 instance

Example vSphere 5.5 Deployment in Transition at Step 4
vCenter Server external deployment with two Platform Services Controller 6.5 instances, two vCenter Server 6.5 instances, and one vCenter Server 6.0 instance

After upgrading the second vCenter Server instance to 6.5, further changes occur in the connectivity between the vCenter Server instances:

Linked Mode functionality is replaced by Enhanced Linked Mode functionality between the newly upgraded vCenter Server 6.5 instances after they are joined to the Platform Services Controller.

The remaining legacy vSphere Web Client instance can no longer view the vCenter Server 6.5 instances.

The legacy vSphere Web Client instance can still view the legacy vCenter Server instances after they are restarted.

The vSphere Web Client 6.5 instances that are part of the newly upgraded vCenter Server 6.5 instances can view the legacy vCenter Server instances and 6.5 instances.

Example vSphere 5.5 Deployment After Step 5 with Upgrade Complete
vCenter Server external deployment with two external Platform Services Controller 6.5 instances and three vCenter Server 6.5 instances

Example vSphere 6.0 Deployment After Step 5 with Upgrade Complete
vCenter Server enternal deployment with two Platform Services Controller 6.5 instances and three vCenter Server 6.5 instances

After upgrading the third and final vCenter Server instance to 6.5, all the vCenter Server instances are connected with full vCenter Server 6.5 functionality.

Enhanced Linked Mode functionality replaces Linked Mode functionality between all the legacy vCenter Server instances after they are joined to the Platform Services Controller 6.5 instances.

The vSphere Web Client 6.5 instances can view all the vCenter Server 6.5 instances.