SR-IOV does not break Live Migration, a technology not covered yet, but allows virtual
machines to move between hosts with no downtime, even when you’re moving a
virtual machine to a host that does not support SR-IOV. Behind the scenes when SR-
IOV is used, the Network Virtualization Service Client (NetVSC) creates two paths for
the virtual machine network adapter inside the VM. One path is via SR-IOV, and one
is via the traditional VMBus path, which uses the Hyper-V switch. When the VM is
running on a host with SR-IOV, the SR-IOV path is used and the VMBus is used only
for control traffic, but if the VM is moved to a host without SR-IOV, then the SR-IOV
path is closed by NetVSC and the VMBus path is used for data and control traffic; this
is all transparent to the virtual machine. It means that you don’t lose any mobility
even when using SR-IOV. To use SR-IOV, both the network adapter and the
motherboard must support it. To use SR-IOV with a virtual switch, the option to use
SR-IOV must be selected at the time of the virtual switch creation, as shown in Figure
3.38. If you’re using the New-VMSwitch cmdlet to create the virtual switch, use the -
EnableIov $True parameter to enable SR-IOV. On the Hardware Acceleration property
tab of the virtual network adapter for a virtual machine that needs to use SR-IOV,
make sure that the Enable SR-IOV check box is selected.
Figure 3.38 Enabling SR-IOV on a virtual switch at creation time
To check your server for SR-IOV support, you can run various commands. To start,
run PowerShell command Get-VMSwitch | Format-List iov as shown in the
following snippet.. Note that this example shows that the network adapter supports
SR-IOV, but it is not supported because of limitations on the server motherboard and
BIOS.
PS C:> Get‐VMSwitch | Format‐List iov
IovEnabled : True
IovSupport : False
IovSupportReasons : {To use SR-IOV on this system, the system BIOS
must be updated to allow Windows to control
PCI Express. Contact your system manufacturer for an update., This system
has a security
vulnerability in the system I/O remapping hardware. As a precaution, the
ability to use
SR-IOV has been disabled. You should contact your system manufacturer for
an updated BIOS
which enables Root Port Alternate Error Delivery mechanism. If all Virtual