A question about nova live-migration across AZ

Laurent Dumont laurentfdumont at gmail.com
Tue Aug 31 02:52:14 UTC 2021


It seems to be the expected behavior from the AZ doc.

https://docs.openstack.org/nova/latest/admin/availability-zones.html

Knowing this, it is dangerous to force a server to another host with
evacuate or live migrate if the server is restricted to a zone and is then
forced to move to a host in another zone, because that will create an
inconsistency in the internal tracking of where that server should live and
may require manually updating the database for that server. For example, if
a user creates a server in zone A and then the admin force live migrates
the server to zone B, and then the user resizes the server, the scheduler
will try to move it back to zone A which may or may not work, e.g. if the
admin deleted or renamed zone A in the interim.


On Mon, Aug 30, 2021 at 9:18 PM Yingji Sun <yingjisun at vmware.com> wrote:

> Buddies,
>
>
>
> I can migration nova instance across available zones with the command
> below. Suppose instance is in AZ1 and host is in AZ2.
>
>
>
> nova --os-compute-api-version 2.67 live-migration --force
> [--block-migrate] <server> [<host>]
>
>
>
> After migration, the instance’s available zone is changed to AZ2.
>
>
>
> However, the available zone information in request_specs was not changed.
>
>
>
> So next time when trying to migrate the instance without specifying a
> target, the migration target will be selected through nova scheduler, by
> the availability zone value (AZ1) saved in request_specs. This caused some
> error.
>
>
>
> Is this an expected behavior ?
>
>
>
> Yingji.
>
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