On 08/05/2014 12:18 PM, Jay Pipes wrote: > Hello stackers, TC, Neutron contributors, > > At the Nova mid-cycle meetup last week in Oregon, during the discussion > 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 the > following specification: > > https://review.openstack.org/#/c/101921/12/specs/juno/neutron-migration.rst > > The above specification outlines a plan to allow migration of *running* > instances from an OpenStack deployment using nova-network (both with and > without multi-host mode) to an OpenStack deployment using Neutron, with > little to no downtime using live migration techniques and an array of > post-vm-migrate strategies to wire up the new VIFs to the Neutron ports. > > 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 downtime > and *really* want to migrate to Neutron. For these deployments, it's > almost guaranteed that they will need to mangle their existing databases > 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 be > very limited. Someone suggested Metacloud *might* be the only deployment > that might meet the needs for a live nova-network -> Neutron migration. > Metacloud folks, please do respond here! > > In short, I don't think the live migration requirement for nova-network > to Neutron is either realistic or valuable, and suggest relaxing it to > be good instructions for cold migration of instances from an older > deployment to a newer deployment. There are other more valuable things > that Neutron contributors could focus on, IMO -- such as the DVR > functionality that brings parity to Neutron with nova-network's > multi-host mode. > > Thoughts? > > -jay > > [1] > https://wiki.openstack.org/wiki/Governance/TechnicalCommittee/Neutron_Gap_Coverage
Yes, I agree with what you're suggesting here. This was the approach I was advocating for a cycle or two ago. In a design summit session, there were folks that seemed to really want to go off and investigate live migration options. Given what has (or hasn't) been done so far, I maintain the same opinion as you've presented here, which is that it's really not a worthwhile investment overall. We should just provide some good documentation on how a cold migration would work. -- Russell Bryant _______________________________________________ OpenStack-dev mailing list OpenStack-dev@lists.openstack.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
