# virtqueue 뒤 QEMU block backend의 세 형태
# Question: Guest /dev/vda 요청이 VM boundary를 넘은 뒤 QEMU에서 qcow2, RAW, Host block device 중 어느 backend로 이어지는가
direction: right
n0: "/dev/vda" {
  shape: cylinder
}
n1: "virtio-blk · virtqueue" {
  shape: rectangle
}
n2: "QEMU block backend" {
  shape: rectangle
}
n3: "qcow2 file" {
  shape: cylinder
}
n4: "RAW file" {
  shape: cylinder
}
n5: "Host block device" {
  shape: cylinder
}
n0 -> n1: "block I/O"
n1 -> n2: "VM boundary"
n2 -> n3: "qcow2 backend"
n2 -> n4: "RAW backend"
n2 -> n5: "block-device backend"