[openstack-dev] [Nova] Migration state machine proposal.

Andrew Laski andrew at lascii.com
Thu Nov 5 15:30:09 UTC 2015


On 11/05/15 at 10:12am, Jonathan D. Proulx wrote:
>On Thu, Nov 05, 2015 at 09:33:37AM -0500, Andrew Laski wrote:
>
>:Can you be a little more specific on what API difference is important
>:to you?  There are two differences currently between migrate and
>:resize in the API:
>:
>:1. There is a different policy check, but this only really protects
>:the next bit.
>:
>:2. Resize passes in a new flavor and migration does not.
>:
>:Both actions result in an instance being scheduled to a new host.  If
>:they were consolidated into a single action with a policy check to
>:enforce that users specified a new flavor and admins could leave that
>:off would that be problematic for you?
>
>My typical use is live-migration (perhaps that is yet another code
>path?) which involves:

Yes, live-migration is completely separate from resize/(cold)migrate.  
I'm not convinced that we can or should consolidate live-migration with 
resize/cold-migrate.

>
>3. specify the host to migrate to
>
>This is what I really want to protect.
>
>my use case if it helps:
>
>The reason I want to specify the host (or if I could even better a
>host aggregaate) is that I use 'cpu_mode=host-passthrough' and have a
>few generations of hardware (and my instance types are not constrained
>to a particular generation which I realize is an option as we do that
>for other purposes) so left to the scheduler it might try to
>live-migrate to an older cpu generation which would fail so we'r
>ecurrently using human intelligence to try to migrate to same
>generation and if that's full move newer.
>
>This is an uncommon but important procedure mostly used for updates that
>require hypervisor reboot in which we roll everything from node-0 to
>node-N, update 0 then roll node-1 to node0 etc ...
>
>If I could constrain migration by host aggregate in ways that didn't
>map to instance type metadata constraints that would simplify this,
>but the current situation is adequate for me.
>
>This isn't an issue with non-live migration or rezize neither of which
>requite CPU consistency.
>
>-Jon
>
>__________________________________________________________________________
>OpenStack Development Mailing List (not for usage questions)
>Unsubscribe: OpenStack-dev-request at lists.openstack.org?subject:unsubscribe
>http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev



More information about the OpenStack-dev mailing list