Attaching Volumes¶
The following sequence diagram outlines the current flow when attaching a
volume to an instance using the os-volume_attachments
API. This diagram
uses the libvirt
driver as an example virt driver to additionally document
the optional interactions with the os-brick
library on the compute hosts
during the request.
Note
os-brick
is not always used to connect volumes to the host, most
notibly when connecting an instance natively to ceph rbd
volumes
The diagram also outlines the various locks taken on the compute during the
attach volume flow. In this example these include locks against the
instance.uuid
, cinder_backend.uuid
orchestrated for nova-compute
by
os-brick
and the generic connect_volume
lock taken within os-brick
itself. This final connect_volume
lock also being held when detaching and
disconnecting a volume from the host by os-brick
.