Roles for Domains

All logical domains are the same and can be distinguished from one another based on the roles that you specify for them. Logical domains can perform the following roles:

• Control domain. The Logical Domains Manager runs in this domain, which enables you to create and manage other logical domains, and to allocate virtual resources to other domains. You can have only one control domain per server. The control domain is the first domain created when you install the Oracle VM Server for SPARC software. The control domain is named primary.

• Service domain. A service domain provides virtual device services to other domains, such as a virtual switch, a virtual console concentrator, and a virtual disk server. You can have more than one service domain, and any domain can be configured as a service domain.

• I/O domain. An I/O domain has direct access to a physical I/O device, such as a network card in a PCI EXPRESS (PCIe) controller. An I/O domain can own the following:

  • A PCIe root complex.

  • A PCIe slot or on-board PCIe device by using the direct I/O (DIO) feature. See Creating an I/O Domain by Assigning PCIe Endpoint Devices.

  • A PCIe SR-IOV virtual function. See Creating an I/O Domain by Using PCIe SR-IOV Virtual Functions.

  An I/O domain can share physical I/O devices with other domains in the form of virtual devices when the I/O domain is also used as a service domain.

• Root domain. A root domain has a PCIe root complex assigned to it. This domain owns the PCIe fabric and provides all fabric-related services, such as fabric error handling. A root domain is also an I/O domain, as it owns and has direct access to physical I/O devices.

  The number of root domains that you can have depends on your platform architecture. For example, if you are using an eight-socket Oracle SPARC T5-8 server, you can have up to 16 root domains.

  The default root domain is the primary domain. You can use non-primary domains to act as root domains.

• Guest domain. A guest domain is a non-I/O domain that consumes virtual device services that are provided by one or more service domains. A guest domain does not have any physical I/O devices but only has virtual I/O devices, such as virtual disks and virtual network interfaces.

You can install the Logical Domains Manager on an existing system that is not already configured with Oracle VM Server for SPARC. In this case, the current instance of the OS becomes the control domain. Also, the system is configured with only one domain, the control domain. After configuring the control domain, you can balance the load of applications across other domains to make the most efficient use of the entire system by adding domains and moving those applications from the control domain to the new domains.