<block_device_template/> is used for creation of new <block_device/>s. It can be found in <mapper/> under <new_targets/>.
New block devices are created by submitting
<block_device_template/> from <new_targets/> of <mapper/>
to Storage Module using “create_bd” function.
<block_device_template/>'s properties and content can be
modified using the same rules before calling “create_bd”
function.
Block Device Template XML description:
<block_device_template/> has the same format as <block_device/>, except that it doesn't have “path” attribute. Path of newly created block device can be extracted from return value of “create_bd” function.