Public bug reported: 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. ** Affects: nova Importance: Undecided Status: New -- 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 OpenStack Compute (nova): New 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/nova/+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