Open Stack

Hi,

we're considering a similar scenario. I don't mean to hijack this  
thread, but would it be possible to migrate to Ubuntu without  
downtime? There are several options I can think of, one that worked  
for us in the past: a reinstallation of the control nodes but keeping  
the database (upgraded in a VM). But this means downtime until at  
least one control node is up and if possible I would like to avoid  
that, so I'm thinking of this:
- Adding compute nodes and install them with Ubuntu Victoria (our  
current version).
- Move the workload away from the other compute nodes and reinstall  
them one by one.

That should work for computes (with cold or live migration). But what  
about the control nodes? We have them in HA setup, would it be  
possible to
- Stop one control node, reinstall it with Ubuntu (Victoria), make  
sure all UIDs/GIDs are the same as before (we use ceph as shared  
storage) so the mounted CephFS still works between the nodes (same for  
the nova live-migration).
- Repeat for other control nodes.

Would those mixed control nodes work together? I will try it anyway in  
a test environment, but I wanted to ask if anybody has tried this  
approach. I'd appreciate any insights.

Thanks,
Eugen


Zitat von Massimo Sgaravatto <massimo.sgaravatto at gmail.com>:

> Ok, thanks a lot
> If cold migration is supposed to work between hosts with different
> operating systems, we are fine
> Cheers, Massimo
>
> On Tue, Dec 6, 2022 at 10:48 AM Sean Mooney <smooney at redhat.com> wrote:
>
>> On Tue, 2022-12-06 at 10:34 +0100, Dmitriy Rabotyagov wrote:
>> > Hi Massimo,
>> >
>> > Assuming you have manual installation (not using any deployment
>> > projects), I have several comments on your plan.
>> >
>> > 1. I've missed when you're going to upgrade Nova/Neutron on computes.
>> > As you should not create a gap in OpenStack versions between
>> > controllers and computes since nova-scheduler has a requirement on RPC
>> > version computes will be using. Or, you must define the rpc version
>> > explicitly in config to have older computes (but it's not really a
>> > suggested way).
>> > 2. Also once you do db sync, your second controller might misbehave
>> > (as some fields could be renamed or new tables must be used), so you
>> > will need to disable it from accepting requests until syncing
>> > openstack version as well. If you're not going to upgrade it until
>> > getting first one to Yoga - it should be disabled all the time until
>> > you get Y services running on it.
>> > 3. It's totally fine to run multi-distro setup. For computes the only
>> > thing that can go wrong is live migrations, and that depends on
>> > libvirt/qemu versions. I'm not sure if CentOS 8 Stream have compatible
>> > version with Ubuntu 22.04 for live migrations to work though, but if
>> > you care about them (I guess you do if you want to migrate workloads
>> > semalessly) - you'd better check. But my guess would be that CentOS 8
>> > Stream should have compatible versions with Ubuntu 20.04 - still needs
>> > deeper checking.
>> the live migration issue is a know limiation
>> basically it wont work across distro today because the qemu emulator path
>> is distro specific and we do not pass that back form the destinatino to the
>> source so libvirt will try and boot the vm referncign a binary that does
>> not exist
>> im sure you could propaly solve that with a symlink or similar.
>> if you did the next issue you would hit is we dont normally allwo live
>> mgration
>> form a newer qemu/libvirt verson to an older one
>>
>> with all that said cold migration shoudl work fine and wihtine any one
>> host os live migration
>> will work. you could proably use host aggreates or simialr to enforece
>> that if needed but
>> cold migration is the best way to move the workloads form hypervior hosts
>> with different distros.
>>
>> >
>> > вт, 6 дек. 2022 г. в 09:40, Massimo Sgaravatto <
>> massimo.sgaravatto at gmail.com>:
>> > >
>> > > Any comments on these questions ?
>> > > Thanks, Massimo
>> > >
>> > > On Fri, Dec 2, 2022 at 5:02 PM Massimo Sgaravatto <
>> massimo.sgaravatto at gmail.com> wrote:
>> > > >
>> > > > Dear all
>> > > >
>> > > >
>> > > >
>> > > > Dear all
>> > > >
>> > > > We are now running an OpenStack deployment: Yoga on CentOS8Stream.
>> > > >
>> > > > We are now thinking about a possible migration to Ubuntu for several
>> reasons in particular:
>> > > >
>> > > > a- 5 years support for both the Operating System and OpenStack
>> (considering LTS releases)
>> > > > b- Possibility do do a clean update between two Ubuntu LTS releases
>> > > > c- Easier procedure (also because of b) for fast forward updates
>> (this is what we use to do)
>> > > >
>> > > > Considering the latter item, my understanding is that an update from
>> Ubuntu 20.04 Ussuri to Ubuntu 22.04 Yoga could be done in the following
>> > > > way (we have two controller nodes and n compute nodes):
>> > > >
>> > > > - Update of first controller node from Ubuntu 20.04 Ussuri to Ubuntu
>> 20.04 Victoria (update OpenStack packages + dbsync)
>> > > > - Update of first controller node from Ubuntu 20.04 Victoria to
>> Ubuntu 20.04 Wallaby (update OpenStack packages + dbsync)
>> > > > - Update of first controller node from Ubuntu 20.04 Wallaby to
>> Ubuntu 20.04 Xena (update OpenStack packages + dbsync)
>> > > > - Update of first controller node from Ubuntu 20.04 Xena to Ubuntu
>> 20.04 Yoga (update OpenStack packages + dbsync)
>> > > > - Update of first controller node from Ubuntu 20.04 Yoga to Ubuntu
>> 22.04 Yoga (update Ubuntu  packages)
>> > > > - Update of second controller node from Ubuntu 20.04 Ussuri to
>> Ubuntu 22.04 Yoga (update OpenStack and Ubuntu packages)
>> > > > - Update of the compute nodes from Ubuntu 20.04 Ussuri to Ubuntu
>> 22.04 Yoga (update OpenStack and Ubuntu packages)
>> > > >
>> > > >
>> > > > We would do the same when migrating from Ubuntu 22.04 Yoga to Ubuntu
>> 24.04 and the OpenStack xyz release (where xyz
>> > > > is the LTS release used in Ubuntu 24.04)
>> > > >
>> > > > Is this supposed to work or am I missing something ?
>> > > >
>> > > > If we decide to migrate to Ubuntu, the first step would be the
>> reinstallation with Ubuntu 22.04/Yoga of each node
>> > > > currently running CentOS8 stream/Yoga.
>> > > > I suppose there are no problems having in the same OpenStack
>> installation nodes running the same
>> > > > Openstack version but different operating systems, or am I wrong ?
>> > > >
>> > > > Thanks, Massimo
>> > > >
>> >
>>
>>