SR-IOV backed networks

You can deploy virtual machines that leverage Single Root Input / Output Virtualization (SR-IOV). SR-IOV supports pass-through of Ethernet data from guest virtual machines directly to hardware. This improves performance by allowing data to pass directly from guest virtual machines to physical adapters with minimal processing between, allowing a guest virtual machine to achieve near wire-speed Ethernet performance. SR-IOV also supports some additional configuration options, such as quality of service (QoS) for enforcing bandwidth allocations to guest virtual machines.

A given SR-IOV adapter can have multiple physical ports, connected to external switches. Each physical port is divided into logical ports. These logical ports are connected to a virtual machine for network connectivity. These logical ports allow a single physical hardware device to appear as multiple devices to guest virtual machines. The following image illustrates the different ways that SR-IOV can be used to connect physical ports to virtual machines.
Figure 1. SR-IOV connectivity options
The image given here depicts the SR-IOV connectivity options

PowerVC can connect a virtual machine that uses an SR-IOV adapter by using options 2, 3 or 4, depending on the specified redundancy levels. Users can implement option 1 outside of PowerVC by carving a virtual function out of a physical port and assigning it as a backing networking device for a Shared Ethernet Adapter (SEA). PowerVC treats that SEA the same as any other SEA, regardless of the backing device.

SR-IOV vs. SEA

In PowerVC, without SR-IOV, you have an SEA and a virtual Ethernet adapter on the Virtual I/O Server (VIOS). These adapters connect to a physical network adapter and to a client network adapter on the virtual machine. This setup allows you to segment your network via VLAN IDs and helps you virtualize your network hardware; providing migration and failover support. An SEA environment also supports higher virtual machine density. However, all network traffic is routed through the SEA on the VIOS, which adds processing cycles.

SR-IOV with vNIC provides a separation of the control plane and data plane for Ethernet within a host. Therefore, an SR-IOV environment performs better because the VIOS is only used to set up and manage the communication channel and provide failover and migration support. SR-IOV does not scale to hundreds or thousands of virtual machines per host. Instead, it is used to set up a few very fast virtual machines.

You can use VLAN IDs to segment your network whether you are using SR-IOV or SEA, but virtual machines cannot be migrated in an SR-IOV environment.

Redundancy support

In the Add network page of GUI, you can choose the Redundant physical network name option for the network. When you deploy a virtual machine with vNIC redundancy option, the redundant adapter is used from the redundant physical network name selected.

When deploying a virtual machine that uses SR-IOV networks, PowerVC creates a vNIC adapter for that virtual machine.

When deploying a virtual machine that uses SR-IOV networks, PowerVC creates a vNIC adapter for that virtual machine. If you select Redundant adapter when deploying a virtual machine, the vNIC adapter created for the virtual machine includes multiple logical ports. These logical ports are isolated as much as possible to provide redundancy by using multiple physical ports, multiple SR-IOV adapters (if possible), and multiple VIOSs (if possible).

Quality of Service

When you create an SR-IOV network, you can use the Virtual NIC capacity field to specify the minimum bandwidth of the network. If that capacity is not available when deploying a virtual machine, the deploy is not allowed.

Deploying, managing, and unmanaging virtual machines

The following takes place when you manage or unmanage a virtual machine that uses an SR-IOV adapter in PowerVC:
  • When a virtual machine is deployed with an SR-IOV interface, or if an SR-IOV network is attached to an existing virtual machine, one or two vNICs are set up on the relevant VIOSs, depending on whether Redundant adapter was selected. That vNIC will be attached to an SR-IOV physical port through newly created logical ports on one side and the vNIC client adapter in a deployed virtual machine.
  • If a virtual machine that uses an SR-IOV network interface is deleted, the corresponding vNICs are removed from Virtual I/O Servers (VIOSs) and the SR-IOV logical ports will be released.
  • You can manage preexisting virtual machines with SR-IOV adapters. If such a virtual machine is brought under PowerVC management, networks are created in PowerVC and attached to the virtual machine.
  • If a virtual machine with an SR-IOV interface is unmanaged, the virtual machine is retained by PowerVM®, and the corresponding network is retained in PowerVC, but is released from use. If the same virtual machine is brought under PowerVC management again, the same port is used, with the same IP address.
  • Before detaching an SR-IOV attached virtual machine, refer to Moving physical I/O devices and slots dynamically in the IBM Power® Knowledge Center for instructions.
  • You can opt to use same VIOSes as SCG for creating a SR-IOV vNIC by using use_vios_from_scg_for_sriov_vnic command. The command allows you to configure the new property in default section of the config file. For details, see CLI commands.