Today, most environments will already contain at least some virtualization. A vSphere design will likely involve upgrading an existing environment to enable new features to meet new requirements for availability, security, performance, and manageability.
The management environment for vSphere has become more complex. The vCenter Server and its components have become a critical part of the environment. In the virtualized data center, the vCenter Server is no longer just a management interface; it also provides provision, availability, security, and other services. Other vSphere and third-party components require vCenter Server to operate correctly. Because of this, upgrading a vCenter Server must be planned correctly.
