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

Paul Carlton paul.carlton2 at hpe.com
Thu Oct 8 09:37:12 UTC 2015

On 08/10/15 09:57, Daniel P. Berrange wrote:
> On Wed, Oct 07, 2015 at 03:54:29PM -0600, Chris Friesen wrote:
>> On 10/07/2015 03:14 AM, Daniel P. Berrange wrote:
>>> For suspended instances, the scenario is really the same as with completely
>>> offline instances. The only extra step is that you need to migrate the saved
>>> image state file, as well as the disk images. This is trivial once you have
>>> done the code for migrating disk images offline, since its "just one more file"
>>> to care about.  Officially apps aren't supposed to know where libvirt keeps
>>> the managed save files, but I think it is fine for Nova to peek behind the
>>> scenes to get them. Alternatively I'd be happy to see an API added to libvirt
>>> to allow the managed save files to be uploaded & downloaded via a libvirt
>>> virStreamPtr object, in the same way we provide APIs to  upload & download
>>> disk volumes. This would avoid the need to know explicitly about the file
>>> location for the managed save image.
>> Assuming we were using libvirt with the storage pools API could we currently
>> (with existing libvirt) migrate domains that have been suspended with
>> virDomainSave()?  Or is the only current option to have nova move the file
>> over using passwordless access?
> If you used virDomainSave() instead of virDomainManagedSave() then you control
> the file location, so you could create a directory based storage pool and
> save the state into that directory, at which point you can use the storag
> pool APIs to upload/download that data.
> Regards,
> Daniel
I will update https://review.openstack.org/#/c/232053
which covers use of libvirt cold migration of non active instances to
cover the use of virDomainSave() and thus allow migration of suspended

Paul Carlton
Software Engineer
Cloud Services
Hewlett Packard
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