Citrix Systems 6 manual Using SR-IOV Enabled NICs, Controlling the rate of outgoing data QoS

If you want to use a storage interface that can be routed from the primary management interface also (bearing in mind that this configuration is not the best practice), you have two options:

•After a host reboot, ensure that the storage interface is correctly configured, and use the xe pbd-unplugand xe pbd-plugcommands to reinitialize the storage connections on the host. This restarts the storage connection and routes it over the correct interface.

•Alternatively, you can use xe pif-forgetto remove the interface from the XenServer database and manually configure it in the control domain. This is an advanced option and requires you to be familiar with how to manually configure Linux networking.

Using SR-IOV Enabled NICs

Single Root I/O Virtualization (SR-IOV) is a PCI device virtualization technology that allows a single PCI device to appear as multiple PCI devices on the physical PCI bus. The actual physical device is known as a Physical Function (PF) while the others are known as Virtual Functions (VF). The purpose of this is for the hypervisor to directly assign one or more of these VFs to a Virtual Machine (VM) using SR-IOV technology: the guest can then use the VF as any other directly assigned PCI device.

Assigning one or more VFs to a VM allows the VM to directly exploit the hardware. When configured, each VM behaves as though it is using the NIC directly, reducing processing overhead and improving performance.

Warning:

If your VM has an SR-IOV VF, functions that require VM mobility, for example, Live Migration, Workload Balancing, Rolling Pool Upgrade, High Availability and Disaster Recovery, are not possible. This is because the VM is directly tied to the physical SR-IOV enabled NIC VF. In addition, VM network traffic sent via an SR-IOV VF bypasses the vSwitch, so it is not possible to create ACLs or view QoS.

Assigning a SR-IOV NIC VF to a VM

Note:

SR-IOV is supported only with SR-IOV enabled NICs listed on the XenServer Hardware Compatibility List and only when used in conjunction with a Windows Server 2008 guest operating system.

1.Open a local command shell on your XenServer host.

2.Run the command lspci to display a list of the Virtual Functions (VF). For example:

07:10.0 Ethernet controller: Intel Corporation 82559 \ Ethernet Controller Virtual Function (rev 01)

In the example above, 07:10.0 is the bus:device.function address of the VF.

3.Assign the required VF to the target VM by running the following commands:

xe vm-param-set other-config:pci=0/0000:<bus:device.function>uuid=<vm-uuid>

4.Start the VM, and install the appropriate VF driver for your specific hardware.

Note:

You can assign multiple VFs to a single VM, however the same VF cannot be shared across multiple VMs.

Controlling the rate of outgoing data (QoS)

To limit the amount of outgoing data a VM can send per second, you can set an optional Quality of Service (QoS) value on VM virtual interfaces (VIFs). The setting lets you specify a maximum transmit rate for outgoing packets in kilobytes per second.

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