Havana libvirt live migration should not be allowed without shared storage, even for volume-backed VMs

Bug #1236356 reported by Nikola Đipanov on 2013-10-07
12
This bug affects 2 people
Affects Status Importance Assigned to Milestone
OpenStack Compute (nova)
High
Nikola Đipanov

Bug Description

The following patch related to bug #1074054 https://review.openstack.org/#/c/17118/ mistakenly allows live migration without shared storage, if the instance is volume backed - only in the libvirt driver.

Bug #1235182 made this issue visible.

this is not the correct thing to do because even though the instance root disk is a cinder volume - the instance might have additional disks that need to be migrated. Currently - nova would just create them on the destination node.

Two possible solutions are:

1) Prevent non-block live migration without shared storage - effectively reverting https://review.openstack.org/#/c/17118/
2) Allow live migration ONLY for volume backed instances that have no local disks. This might be a preferred way of solving the issue, as there is value in having the flexibility to have live migrations without the overhead of setting up shared storage for volume-only VMs

Changed in nova:
importance: Undecided → High
Edward Hope-Morley (hopem) wrote :

non-local ephemeral disk support was recently added to Nova (https://review.openstack.org/#/c/36042/24) so I think there is a valid case for allowing live-migration without having shared storage on compute nodes.

Nikola Đipanov (ndipanov) wrote :

In reply to Edwaeds comment #1:

Most of the issues around this were discussed on the review that brought this bug to light: https://review.openstack.org/#/c/49816/ so anyone interested should consider reading through that as well.

tags: added: havana-rc-potential
Mathew Odden (locke105) on 2013-10-08
Changed in nova:
status: New → Triaged
Russell Bryant (russellb) wrote :
Changed in nova:
status: Triaged → In Progress
milestone: none → havana-rc2
assignee: nobody → Nikola Đipanov (ndipanov)

Reviewed: https://review.openstack.org/50982
Committed: http://github.com/openstack/nova/commit/cf89e78a1b921adee5b1943600315b0637fdefdc
Submitter: Jenkins
Branch: master

commit cf89e78a1b921adee5b1943600315b0637fdefdc
Author: Nikola Dipanov <email address hidden>
Date: Thu Oct 10 16:00:26 2013 +0200

    Libvirt: disallow live-mig for volume-backed with local disk

    This patch makes libvirt raise an error if a live migration was
    requested without shared storage for a volume-backed instance, if that
    instance has any local disks.

    The reason is that without shared storage, local disks will be
    re-created on the destination node which can result in loss of data.

    Change-Id: Ic96dabf6020e957309280862b325792faf44b1f5
    Closes-bug: 1236356

Changed in nova:
status: In Progress → Fix Committed

Reviewed: https://review.openstack.org/51316
Committed: http://github.com/openstack/nova/commit/c63f4af000af191a9a70b6b62dbda40a5c9b59e5
Submitter: Jenkins
Branch: milestone-proposed

commit c63f4af000af191a9a70b6b62dbda40a5c9b59e5
Author: Nikola Dipanov <email address hidden>
Date: Thu Oct 10 16:00:26 2013 +0200

    Libvirt: disallow live-mig for volume-backed with local disk

    This patch makes libvirt raise an error if a live migration was
    requested without shared storage for a volume-backed instance, if that
    instance has any local disks.

    The reason is that without shared storage, local disks will be
    re-created on the destination node which can result in loss of data.

    Change-Id: Ic96dabf6020e957309280862b325792faf44b1f5
    Closes-bug: 1236356
    (cherry picked from commit cf89e78a1b921adee5b1943600315b0637fdefdc)

Changed in nova:
status: Fix Committed → Fix Released
Thierry Carrez (ttx) on 2013-10-17
Changed in nova:
milestone: havana-rc2 → 2013.2
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