[openstack-dev] [nova][ironic] Instance can "migrate" to another node?

c1 c1_dx at yahoo.com
Sat Nov 5 01:51:17 UTC 2016

Message: 7
Date: Thu, 3 Nov 2016 16:50:54 +0000
From: Jay Faulkner <jay at jvf.cc <mailto:jay at jvf.cc>>
To: "OpenStack Development Mailing List (not for usage questions)"
	<openstack-dev at lists.openstack.org <mailto:openstack-dev at lists.openstack.org>>
Subject: Re: [openstack-dev] [nova][ironic] Instance can "migrate" to
	another node?
Message-ID: <1417F96D-BEA5-457A-BA27-96511CBCB422 at jvf.cc <mailto:1417F96D-BEA5-457A-BA27-96511CBCB422 at jvf.cc>>
Content-Type: text/plain; charset="utf-8”

Thanks a lot, this very helpful for me.

> Hey, 
> This is all detailed in the release notes for nova here: http://docs.openstack.org/releasenotes/nova/newton.html#new-features <http://docs.openstack.org/releasenotes/nova/newton.html#new-features> ? just search for ?Ironic?.
> Here is the relevant section:
> "Note that instances will still be owned by the same nova-compute service for the entire life of the instance, and so the ironic node that instance is on will also be managed by the same nova-compute service until the node is deleted. This also means that removing a nova-compute service will leave instances managed by that service orphaned, and as such most instance actions will not work until a nova-compute service with the same hostname is brought (back) online.
> When nova-compute services are brought up or down, the ring will eventually re-balance (when the resource tracker runs on each compute). This may result in duplicate compute_node entries for ironic nodes while the nova-compute service pool is re-balancing. However, because any nova-compute service running the ironic virt driver can manage any ironic node, if a build request goes to the compute service not currently managing the node the build request is for, it will still succeed.?
> So essentially what this means is that for provisioned instances, there?s no way to migrate them off of a failed compute host, but unprovisioned node capacity will rebalance automatically between compute hosts when you provision a new one. Essentially if you have a nova compute host fail but want to be able to continue managing instances deployed by it, you?ll have to build another nova-compute host with the same hostname (or CONF.host setting) in order to do anything beyond deleting it.
> Hope this helps,
> Jay Faulkner
>> On Nov 3, 2016, at 3:12 AM, c1 <c1_dx at yahoo.com <mailto:c1_dx at yahoo.com>> wrote:
>> Hi al,
>> Now, nova?s ironic driver can allow multiple compute services.
>> I am not sure that, when a compute node is down. 
>> The instances running in it, whether can ?migrate? to another compute node(use ironic driver)?
>> Thanks
>> C1dx 
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