[openstack-dev] [nova][cinder] nova support for volume multiattach

Matt Riedemann mriedemos at gmail.com
Thu Jan 11 00:13:33 UTC 2018

Hi everyone,

I wanted to point out that the nova API patch for volume mulitattach 
support is available for review:


It's actually a series of changes, but that is the last one that enables 
the feature in nova. It relies on the 2.59 compute API microversion to 
be able to create a server from a mulitattach volume or to attach a 
mulitattach volume to a server.

We do not allow attaching a mulitattach volume to a shelved offloaded 
server, to be consistent with the 2.49 microversion for tagged attach.

When creating a server from a mulitattach volume, the compute API will 
check to see that all nova-compute services in the deployment have been 
upgraded to the service version that supports the mulitattach code in 
the libvirt driver.

Similarly, when attaching a mulitattach volume to an existing server 
instance, the compute API will check that the compute hosting the 
instance is new enough to support mulitattach volumes (has been 
upgraded) and it's using a virt driver that supports the capability 
(currently only the libvirt driver).

There are more details in the release note but I wanted to point out 
those restrictions.

There is also a set of tempest integration tests here:


Those will be tested in the nova-multiattach CI job:


Due to restrictions with libvirt, mulitattach support is only available 
if qemu<2.10 or libvirt>=3.10. The test environment takes this into 
account for upstream testing.

Nova will rely on Cinder microversion >=3.44, which was added in Queens, 
for safe detach of a mulitattach volume.

There is a design spec for Cinder which describes how volume mulitattach 
will be supported in Cinder and how operators will be able to configure 
volume types and Cinder policy rules for mulitattach support:


Several people from various companies have been pushing this hard in the 
Queens release and we're two weeks away from feature freeze. I'm on 
vacation next week also, but I have a feeling that this will get done 
finally in Queens.




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