Snapshots are taken of VMs prior to upgrading so those machines can be reverted back in case there is a problem with the applied patches.
Solution providers can run v Center Update Manager on Windows workstations, and the Update Manager consists of several components, including the plug-in component to the v Sphere Client, a Windows service that can run on the v Center Server and a database that stores patch metadata and other information.
Solution providers can also use the utility with v Sphere to upgrade ESX 3.x hosts to ESX 4.x hosts.
However, with the recently released v Sphere 4.1, the Host Update Utility is no longer bundled with the v Sphere Client.

Solution providers can use v Center Update Manager for VMs running Windows or Linux operating systems (OSes).
These ports will not conflict with v Center Server ports if you install them at the same time.
Finally, you will be prompted for a location to install the Update Manager application along with a separate location to use for patching and updating storage.
Solution providers that use the existing v Center Server database can select the existing Open Database Connectivity (ODBC) connection, otherwise they will have to create a new ODBC connection to which ever database is in use.
Next, you will have to choose which port to use for Update Manager; normally, the defaults are fine and you don't want to change them.