Message: 7
Date: Thu, 3 Nov 2016 16:50:54 +0000
From: Jay Faulkner <[email protected] <mailto:[email protected]>>
To: "OpenStack Development Mailing List (not for usage questions)"
        <[email protected] 
<mailto:[email protected]>>
Subject: Re: [openstack-dev] [nova][ironic] Instance can "migrate" to
        another node?
Message-ID: <[email protected] 
<mailto:[email protected]>>
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
> OSIC
> 
>> On Nov 3, 2016, at 3:12 AM, c1 <[email protected] <mailto:[email protected]>> 
>> 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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