When you install or upgrade vCenter Server and Platform Services Controller on Windows, the installer does a pre-check, for example, to verify that enough space is available on the virtual machine or physical server where you are installing or upgrading vCenter Server, and verifies that the external database, if any, can be successfully accessed.
When you upgrade vCenter Single Sign-On (version 5.5) or Platform Services Controller (version 6.0) vCenter Single Sign-On is included as part of the Platform Services Controller. During the upgrade of an external Platform Services Controller, the installer provides you with the option to upgrade the existing vCenter Single Sign-On server domain. During the upgrade of vCenter Server with an external Platform Services Controller, the installer prompts you to join an existing vCenter Single Sign-On server domain. When you provide the information about the vCenter Single Sign-On service, the installer uses the administrator account to check the host name and password, to verify that the details of the vCenter Single Sign-On server you provided can be authenticated before proceeding with the upgrade process.
The pre-upgrade checker performs checks for the following aspects of the environment:
Minimum processor requirements
Minimum memory requirements
Minimum disk space requirements
Permissions on the selected install and data directory
Internal and external port availability
External database version
External database connectivity
Administrator privileges on the Windows machine
Any credentials that you enter
For information about the minimum storage requirements, see Storage Requirements for vCenter Server and Platform Services Controller on Windows. For information about the minimum hardware requirements, see Hardware Requirements for vCenter Server and Platform Services Controller on Windows.