filename    : 'gluster://gluster-host/vol0/img1'
format node : '#block1008'
storage node: '#block981'
backingfile : 'gluster://gluster-host/vol0/img0'
backing ptr : '#block349'
  filename    : 'gluster://gluster-host/vol0/img0'
  format node : '#block349'
  storage node: '#block269'
  backingfile : '<null>'
  backing ptr : '<null>'