Not all Oracle VM Servers within a server pool may be required for the purpose of running virtual machines. Oracle VM Servers are also required to perform utility functions, including performing actions on storage repositories on behalf of Oracle VM Manager. While all Oracle VM Servers can be configured to be capable of performing both functions, Oracle VM provides the option to separate servers within a server pool based on their functional roles. These roles are defined as follows:
VM Server role: The VM Server role enables an Oracle VM Server to run virtual machines.
Utility Server role: A Utility Server will be favored to do operations other than hosting virtual machines, for example, importing virtual machine templates and assemblies, creating virtual machine templates from assemblies, and creating repositories. If no Utility Servers are available, a non-utility server is chosen to do the work.
The role of a server can be configured within Oracle VM Manager once the server is part of a server pool. At least one server within the server pool must be assigned the VM Server role, or no virtual machines are able to run in the server pool. When you add an Oracle VM Server to a server pool it has both the Utility Server role and the VM Server role automatically selected by default. The VM Server role is required to run virtual machines. The Utility Server role is not required, it is advisory only.
Since Oracle VM Servers are capable of being configured for either or both roles, role separation is used for performance purposes. For instance, in the case of the import of a virtual machine template or assembly, it is preferable that there is a server dedicated to this task, to reduce the impact of such a task on the running of virtual machines within the server pool.
You cannot update the VM Server role for an Oracle VM Server if the server is not in a server pool or if the Oracle VM Server has any virtual machines, running or not running. You must own the Oracle VM Server to change the VM Server role. You can change the Utility Server role anytime as long as you own the Oracle VM Server.
More information about the configuration of server roles can be found at Edit Server in the Oracle VM Manager User's Guide.