Manila shares can have one or more export locations. The exact number
depends on the driver and the storage controller, and there is no
preference for more or fewer export locations. Usually drivers create an
export location for each physical network interface through which the
share can be accessed.

Because not all export locations have the same qualities, Manila
allows drivers to add additional keys to the dict returned for each
export location when a share is created. The share manager stores these
extra keys and values in the database and they are available to the API
service, which may expose them through the REST API or use them for
filtering.

Metadata Keys

Only keys defined in this document are valid. Arbitrary
driver-defined keys are not allowed. The following keys are defined:

• is_admin_only – May be True or False.
  Defaults to False. Indicates that the export location exists for
  administrative purposes. If is_admin_only=True, then the export location
  is hidden from non-admin users calling the REST API. Also, these export
  locations are assumed to be reachable directly from the admin network,
  which is important for drivers that support share servers and which have
  some export locations only accessible to tenants.
• preferred – May be True or False.
  Defaults to False. Indicates that clients should prefer to mount this
  export location over other export locations that are not preferred. This
  may be used by drivers which have fast/slow paths to indicate to clients
  which paths are faster. It could be used to indicate a path is preferred
  for another reason, as long as the reason isn’t one that changes over
  the life of the manila-share service. This key is always visible through
  the REST API.