filename    : '/var/lib/libvirt/images/a.qcow2'
format node : '#block170'
storage node: '#block057'
backingfile : '/var/lib/libvirt/images/base.qcow2'
backing ptr : '<null>'

filename    : '/var/lib/libvirt/images/b.qcow2'
format node : '#block574'
storage node: '#block405'
backingfile : '/var/lib/libvirt/images/base.qcow2'
backing ptr : '<null>'