Logical Domains Manager

The Logical Domains Manager is used to create and manage logical domains, as well as map logical domains to physical resources. Only one Logical Domains Manager can run on a server.

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. The following are the roles that logical domains can perform:

• 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. 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 a PCIe root complex, or it can own a PCIe slot or on-board PCIe device by using the direct I/O (DIO) feature. See Assigning PCIe Endpoint Devices.

  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 a Sun SPARC Enterprise T5440 server, you can have up to four 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 Logical Domains. 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. You do this by adding domains and moving those applications from the control domain to the new domains.

Command-Line Interface

The Logical Domains Manager uses a command-line interface (CLI) to create and configure logical domains. The CLI is a single command, ldm, that has multiple subcommands. See the ldm(1M) man page.

The Logical Domains Manager daemon, ldmd, must be running to use the Logical Domains Manager CLI.

Virtual Input/Output

In a Logical Domains environment, you can provision up to 128 domains on an UltraSPARC T2 Plus processor system and a SPARC T3 processor system. These systems have a limited number of I/O buses and physical I/O slots. As a result, you cannot provide exclusive access to a physical disk and network devices to all domains on these systems. You can assign a PCIe bus or endpoint device to a domain to provide it with access to a physical device. Note that this solution is insufficient to provide all domains with exclusive device access. See Chapter 6, Setting Up I/O Domains. This limitation on the number of physical I/O devices that can be directly accessed is addressed by implementing a virtualized I/O model.

Any logical domains that have no physical I/O access are configured with virtual I/O devices that communicate with a service domain. The service domain runs a virtual device service to provide access to a physical device or to its functions. In this client-server model, virtual I/O devices either communicate with each other or with a service counterpart through interdomain communication channels called logical domain channels (LDCs). The virtualized I/O functionality includes support for virtual networking, storage, and consoles.

Virtual Network

Logical Domains uses the virtual network device and virtual network switch device to implement virtual networking. The virtual network (vnet) device emulates an Ethernet device and communicates with other vnet devices in the system by using a point-to-point channel. The virtual switch (vsw) device primarily functions as a multiplexor of all the virtual network's incoming and outgoing packets. The vsw device interfaces directly with a physical network adapter on a service domain, and sends and receives packets on behalf of a virtual network. The vsw device also functions as a simple layer-2 switch and switches packets between the vnet devices connected to it within the system.

Virtual Storage

The virtual storage infrastructure uses a client-server model to enable logical domains to access block-level storage that is not directly assigned to them. The model uses the following components:

• Virtual disk client (vdc) that exports a block device interface

• Virtual disk service (vds) that processes disk requests on behalf of the virtual disk client and submits them to the back-end storage that resides on the service domain

Although the virtual disks appear as regular disks on the client domain, most disk operations are forwarded to the virtual disk service and processed on the service domain.

Virtual Console

In a Logical Domains environment, console I/O from the primary domain is directed to the service processor. The console I/O from all other domains is redirected to the service domain that is running the virtual console concentrator (vcc). The domain that runs the vcc is typically the primary domain. The virtual console concentrator service functions as a concentrator for all domains' console traffic, and interfaces with the virtual network terminal server daemon (vntsd) to provide access to each console through a UNIX socket.

Resource Configuration

A system that runs the Oracle VM Server for SPARC software can configure resources, such as virtual CPUs, virtual I/O devices, cryptographic units, and memory. Some resources can be configured dynamically on a running domain, while others must be configured on a stopped domain. If a resource cannot be dynamically configured on the control domain, you must first initiate a delayed reconfiguration. The delayed reconfiguration postpones the configuration activities until after the control domain has been rebooted. For more information, see Resource Reconfiguration.

Persistent Configurations

You can use the ldm command to store the current configuration of a logical domain on the service processor. You can add a configuration, specify a configuration to be used, remove a configuration, and list the configurations. See the ldm(1M) man page. You can also specify a configuration to boot from the SP. See Using Logical Domains With the Service Processor.

For information about managing configurations, see Managing Logical Domains Configurations.