As mentioned in the mailing list, I think this is also something to be controlled in Cinder during retype or volume live migration since that would be a fast fail for this scenario:
http://lists.openstack.org/pipermail/openstack-dev/2018-June/131234.html Otherwise cinder calls swap volume in nova, which will fail back to cinder, and then cinder has to rollback; it's just easier to fail fast in the cinder API. ** Changed in: nova Assignee: (unassigned) => Matt Riedemann (mriedem) ** Changed in: nova Status: New => In Progress ** Changed in: nova Importance: Undecided => High ** Tags added: libvirt multiattach volumes ** Also affects: cinder Importance: Undecided Status: New ** Also affects: nova/queens Importance: Undecided Status: New ** Changed in: nova/queens Status: New => Triaged ** Changed in: nova/queens Importance: Undecided => High -- You received this bug notification because you are a member of Yahoo! Engineering Team, which is subscribed to OpenStack Compute (nova). https://bugs.launchpad.net/bugs/1775418 Title: Swap volume of multiattached volume will corrupt data Status in Cinder: New Status in OpenStack Compute (nova): In Progress Status in OpenStack Compute (nova) queens series: Triaged Bug description: We currently permit the following: Create multiattach volumes a and b Create servers 1 and 2 Attach volume a to servers 1 and 2 swap_volume(server 1, volume a, volume b) In fact, we have a tempest test which tests exactly this sequence: api.compute.admin.test_volume_swap.TestMultiAttachVolumeSwap.test_volume_swap_with_multiattach The problem is that writes from server 2 during the copy operation on server 1 will continue to hit the underlying storage, but as server 1 doesn't know about them they won't be reflected on the copy on volume b. This will lead to an inconsistent copy, and therefore data corruption on volume b. Also, this whole flow makes no sense for a multiattached volume because even if we managed a consistent copy all we've achieved is forking our data between the 2 volumes. The purpose of this call is to allow the operator to move volumes. We need a fundamentally different approach for multiattached volumes. In the short term we should at least prevent data corruption by preventing swap volume of a multiattached volume. This would also cause the above tempest test to fail, but as I don't believe it's possible to implement the test safely this would be correct. To manage notifications about this bug go to: https://bugs.launchpad.net/cinder/+bug/1775418/+subscriptions -- Mailing list: https://launchpad.net/~yahoo-eng-team Post to : yahoo-eng-team@lists.launchpad.net Unsubscribe : https://launchpad.net/~yahoo-eng-team More help : https://help.launchpad.net/ListHelp