[openstack-dev] [nova] live migration in Mitaka

Chris Friesen chris.friesen at windriver.com
Tue Oct 6 17:43:52 UTC 2015

On 10/06/2015 11:27 AM, Paul Carlton wrote:
> On 06/10/15 17:30, Chris Friesen wrote:
>> On 10/06/2015 08:11 AM, Daniel P. Berrange wrote:
>>> On Tue, Oct 06, 2015 at 02:54:21PM +0100, Paul Carlton wrote:
>>>> https://review.openstack.org/#/c/85048/ was raised to address the
>>>> migration of instances that are not running but people did not warm to
>>>> the idea of bringing a stopped/suspended instance to a paused state to
>>>> migrate it.  Is there any work in progress to get libvirt enhanced to
>>>> perform the migration of non active virtual machines?
>>> Libvirt can "migrate" the configuration of an inactive VM, but does
>>> not plan todo anything related to storage migration. OpenStack could
>>> already solve this itself by using libvirt storage pool APIs to
>>> copy storage volumes across, but the storage pool worked in Nova
>>> is stalled
>>> https://review.openstack.org/#/q/status:abandoned+project:openstack/nova+branch:master+topic:bp/use-libvirt-storage-pools,n,z
>> What is the libvirt API to migrate a paused/suspended VM? Currently nova uses
>> dom.managedSave(), so it doesn't know what file libvirt used to save the
>> state.  Can libvirt migrate that file transparently?
>> I had thought we might switch to virDomainSave() and then use the cold
>> migration framework, but that requires passwordless ssh.  If there's a way to
>> get libvirt to handle it internally via the storage pool API then that would
>> be better.

> So my reading of this is the issue could be addressed in Mitaka by
> implementing
> http://specs.openstack.org/openstack/nova-specs/specs/kilo/approved/use-libvirt-storage-pools.html
> and
> https://review.openstack.org/#/c/126979/4/specs/kilo/approved/migrate-libvirt-volumes.rst
> is there any prospect of this being progressed?

Paul, that would avoid the need for cold migrations to use passwordless ssh 
between nodes.  However, I think there may be additional work to handle 
migrating paused/suspended instances--still waiting for Daniel to address that bit.


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