What happens if a virtual machine is not set to use virtio?

When a virtual machine is not set to use virtio, one significant consequence is that it could experience decreased network performance. Virtio is a virtualization standard that provides a high-performance interface for virtualized devices. By default, if a virtual machine is not configured to use virtio for its network and disk interfaces, it may instead default to emulated hardware drivers. These emulated drivers are less efficient because they translate virtual device requests into actual hardware calls, leading to higher overhead and increased latency.

In contrast, using virtio allows for more direct communication between the virtual machine and the hypervisor, reducing overhead and improving performance. Therefore, omitting virtio can lead to bottlenecks in processing network data, making it a suboptimal setup for workloads that require efficient networking.

The other options, while they might present potential concerns, do not accurately characterize the main consequence of not using virtio. For instance, a virtual machine may still connect to the network using alternative drivers, but its performance will be subpar compared to using virtio. Similarly, disk space usage typically remains unaffected solely by the driver type and is more influenced by the configuration and workload of the VM itself.