7.7.3. Adding a vNIC Backing Device

A vNIC adapter can have more than one vNIC backing device for higher availability. If a logical SR-IOV port fails (link down or failure of the virtual I/O server), the next vNIC backing device and its associated logical SR-IOV port takes over. Only one of the vNIC backing devices (logical SR-IOV port) is active at any one time. Figure 7.21 shows a client LPAR with a vNIC adapter and 2 vNIC backing devices. Two physical SR-IOV ports are connected to the same external network. For maximum redundancy, the two vNIC backing devices are created on two different virtual I/O servers. Regardless of whether a physical Ethernet link fails or a virtual I/O server fails, a vNIC failover can always be made to a functioning combination of virtual I/O server and logical SR-IOV port. The vNIC backing devices monitor the status of the logical SR-IOV ports and report this regularly to the hypervisor in the form of heartbeats. In the event of a failure, the POWER hypervisor decides which vNIC backing device that is still functioning is activated.

vNIC adapter with 2 vNIC backing devices and vNIC failover.
Figure 7.21: vNIC adapter with 2 vNIC backing devices and vNIC failover.

Each vNIC backing device has a configurable failover priority (attribute failover_priority). This can have values between 1 and 100, whereby a lower value means a higher priority. The default failover priority is 50. In the event of an error, the hypervisor selects the vNIC backing device with the highest failover priority (lowest value) as the new active vNIC backing device.

A vNIC backing device can be added to a vNIC adapter with the command “lpar addvnicbkdev” (add vNIC backing device):

$ lpar addvnicbkdev aix22 6 ms03-vio2 C6-T1

The vNIC adapter in slot 6 of aix22 now has 2 vNIC backing devices. This protects the vNIC adapter against the failure of a vNIC backing device. If the active vNIC backing device fails, a vNIC failover is carried out to the second vNIC backing device.

$ lpar lsvnic -a aix22
                           FAILOVER                                      PHYS  LOGICAL   CURRENT     MAX  
aix22  6     Yes       50        1     Operational  ms03-vio1  1        0     27004005  2.0       100.0
aix22  6     Yes       50        0     Operational  ms03-vio2  2        0     27008004  2.0       100.0

The output shows that the vNIC backing device for the logical SR-IOV port 27004005 is currently the active device (value 1 in the ACTV column). Both vNIC backing devices have the status Operational and both have the same value for the failover priority.

Note: Two vNIC backing devices of the same vNIC adapter cannot use logical ports that belong to the same physical port! If the physical link of such a physical port were to go down (link down), both vNIC backing devices would fail at the same time.