[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
instances.

-- 
Paul Carlton
Software Engineer
Cloud Services
Hewlett Packard
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