[openstack-dev] [Nova][Neutron][Technical Committee] nova-network -> Neutron. Throwing a wrench in the Neutron gap analysis

Mike Spreitzer mspreitz at us.ibm.com
Tue Aug 5 16:34:46 UTC 2014

Monty Taylor <mordred at inaugust.com> wrote on 08/05/2014 12:27:14 PM:

> On 08/05/2014 09:18 AM, Jay Pipes wrote:
> > Hello stackers, TC, Neutron contributors,
> >
> > At the Nova mid-cycle meetup last week in Oregon, during the 
> > about the future of nova-network, the topic of nova-network -> Neutron
> > migration came up.
> >
> > For some reason, I had been clueless about the details of one of the
> > items in the gap analysis the TC had requested [1]. Namely, the 5th
> > item, about nova-network -> Neutron migration, which is detailed in 
> > following specification:
> >
> > 

> >
> > ...
> >
> > I personally believe that this requirement to support a live migration
> > with no downtime of running instances between a nova-network and a
> > Neutron deployment *is neither realistic, nor worth the extensive time
> > and technical debt needed to make this happen*.
> >
> > I suggest that it would be better to instead provide good instructions
> > for doing cold migration (snapshot VMs in old nova-network deployment,
> > store in Swift or something, then launch VM from a snapshot in new
> > Neutron deployment) -- which should cover the majority of deployments 
> > and then write some instructions for what to look out for when doing a
> > custom migration for environments that simply cannot afford any 
> > and *really* want to migrate to Neutron. For these deployments, it's
> > almost guaranteed that they will need to mangle their existing 
> > and do manual data migration anyway -- like RAX did when moving from
> > nova-network to Neutron. The variables are too many to list here, and
> > the number of deployments actually *needing* this work seems to me to 
> > very limited. Someone suggested Metacloud *might* be the only 
> > that might meet the needs for a live nova-network -> Neutron 
> > Metacloud folks, please do respond here!
> >
> > ...
> I agree 100%. Although I understand the I think it's an unreasonably 
> high burden in an area where there are many many other real pressing 
> issues that need to be solved.

I will go a little further.  My focus is on workloads that are composed of 
scaling groups (one strict way of saying "cattle not pets").  In this case 
I do not need to migrate individual Compute instances, just shut down 
obsolete ones and start shiny new ones.


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