GlusterFS is a distributed storage system. virtio-fs is a shared file systems for virtual machines. You can expose GlusterFS directory trees to virtual machin

GlusterFS is a distributed storage system. virtio-fs is a shared file systems for virtual machines. You can expose GlusterFS directory trees to virtual machines using virtio-fs but virtio-fs itself doesn't do the network communication or policy decisions about where and how data is stored on the network - that's the job of GlusterFS. The reason you might want to use both together is to hide the details of the GlusterFS configuration from the virtual machine. That way the virtual machine only sees a virtio-fs device and doesn't have network access to your GlusterFS cluster.