Virtio-net failover is a virtualization technology that allows a virtual machine (VM) to switch from a Virtual Function I/O (VFIO) device to a virtio-net device when the VM needs to be migrated from a host to another.
On one hand, the Single Root I/O Virtualization (SR-IOV) technology allows a device like a networking card to be split into several devices (the Virtual Functions) and with the help of the VFIO technology, the kernel of the VM can directly drive these devices. This is interesting in terms of performance, because it can reach the same level as a bare metal system. In this case, the cost of the performance is that a VFIO device cannot be migrated.
On the other hand, virtio-net is a paravirtualized networking device that has good performance and can be migrated. The trade off is that performance is not as good as with VFIO devices.
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