On 06/08/14 13:30, Robert Collins wrote:
On 6 August 2014 17:27, Tom Fifield <t...@openstack.org> wrote:
On 06/08/14 13:24, Robert Collins wrote:

What happened to your DB migrations then? :)

Sorry if I misunderstood, I thought we were talking about running VM
downtime here?

While DB migrations are running things like the nova metadata service
can/will misbehave - and user code within instances will be affected.
Thats arguably VM downtime.

OTOH you could define it more narrowly as 'VMs are not powered off' or
'VMs are not stalled for more than 2s without a time slice' etc etc -
my sense is that most users are going to be particularly concerned
about things for which they have to *do something* - e.g. VMs being
powered off or rebooted - but having no network for a short period
while vifs are replugged and the overlay network re-establishes itself
would be much less concerning.

I think you've got it there, Rob - nicely put :)

In many cases the users I've spoken to who are looking for a live path out of nova-network on to neutron are actually completely OK with some "API service" downtime (metadata service is an API service by their definition). A little 'glitch' in the network is also OK for many of them.

Contrast that with the original proposal in this thread ("snapshot VMs in old nova-network deployment, store in Swift or something, then launch VM from a snapshot in new Neutron deployment") - it is completely unacceptable and is not considered a migration path for these users.



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