[openstack-dev] [nova][cell] Can nova do live migration cross cells?

John Garbutt john at johngarbutt.com
Fri Jan 8 12:33:34 UTC 2016

On 8 January 2016 at 08:17, 少合冯 <lvmxhster at gmail.com> wrote:
> Hi, all
> Now I'm working on the migrations list/show API.
> The new api defines  migrations is a sub-collection of an instance.
> GET   v2.1/tenant_id/servers/server-id/migrations/migration-id
> I need to support  the new cell API to get a migration of a specified
> instance.
> get_migration_by_instance_and_id
> I read up the nova cell doc.
> http://docs.openstack.org/developer/nova/cells.html
> It tells us that, the migrations table will be API-level.
> The instances table is Cell-level.
> So does that means that we can do live migration cross cells?

In sort, you can't currently live-migrate between cells.

So there is the current cells v1. When using cells v1 you will never
be able to move between cells. In addition, when using nova-network,
network assumptions generally mean IPs can't move between cells.

In cells v2, we were talking about ways that could happen. Its still
hard, because you would need to copy the instance record between one
cell database to another, with the API understanding how the move is
going. Complexity best avoided, if possible.

> And also this will affect my code.
> If the migrations is API-level, so I do not need a cell name to get the
> migrations info from DB.
> Or I need to get the cell name by the specified instance, and then get the
> migrations info by _TargetedMessage.

Afraid I don't have enough context from the rest of your email to
answer these questions.


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