(
  source only properties:
  {
    "driver": "rbd",
    "pool": "rbdpool",
    "image": "rbdimg",
    "server": [
      {
        "host": "host1.example.com",
        "port": "0"
      },
      {
        "host": "host2.example.com",
        "port": "0"
      }
    ]
  }
  backing store string:
  json:{"file":{
    "driver": "rbd",
    "pool": "rbdpool",
    "image": "rbdimg",
    "server": [
      {
        "host": "host1.example.com",
        "port": "0"
      },
      {
        "host": "host2.example.com",
        "port": "0"
      }
    ]
  }
  }
)
(
  source only properties:
  {
    "driver": "iscsi",
    "portal": "example.org:3260",
    "target": "iqn.2016-09.com.example:iscsitarget",
    "lun": 1,
    "transport": "tcp"
  }
  backing store string:
  iscsi://example.org:3260/iqn.2016-09.com.example%3Aiscsitarget/1
)