---
features:
  - |
    This release adds support to attach a volume to multiple
    server instances. The feature can only be used in Nova if the
    volume is created in Cinder with the **multiattach** flag set
    to True. It is the responsibility of the user to use a
    proper filesystem in the guest that supports shared read/write access.

    This feature is currently only supported by the libvirt compute driver
    and only then if qemu<2.10 or libvirt>3.10 on the compute host.

    API restrictions:

    * Compute API microversion 2.60 must be used to create a server from
      a multiattach volume or to attach a multiattach volume to an existing
      server instance.
    * When creating a server using a multiattach volume, the API will check
      if the compute services have all been upgraded to a minimum level of
      support and will fail with a 409 HTTPConflict response if the computes
      are not yet upgraded.
    * Attaching a multiattach volume to a shelved offloaded instance is not
      supported and will result in a 400 HTTPBadRequest response.
    * Attaching a multiattach volume to an existing server instance will check
      that the compute hosting that instance is new enough to support it and
      has the capability to support it. If the compute cannot support the
      multiattach volume, a 409 HTTPConflict response is returned.

    See the `Cinder enable multiattach`_ spec for details on configuring
    Cinder for multiattach support.

    .. _Cinder enable multiattach: https://specs.openstack.org/openstack/cinder-specs/specs/queens/enable-multiattach.html
