[cinder][nova] Migrating servers' root block devices from a cinder backend to another

Tony Pearce tony.pearce at cinglevue.com
Thu Jan 30 09:58:21 UTC 2020


Thanks Tobias - thats my last resort. I'd still need to upload that image
to the new openstack and then build an instance from the image. I'd also
need to use metadata to make sure the instance was built with the same
components (IP address etc).


*Tony Pearce*   |
*Senior Network Engineer / Infrastructure Lead**Cinglevue International
<https://www.cinglevue.com>*

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On Thu, 30 Jan 2020 at 17:55, Tobias Urdin <tobias.urdin at binero.se> wrote:

> Another approach would be to export the data to Glance and download then
> you can upload it somewhere.
>
> There is no ready thing that I know about. We used the openstacksdk to
> simply recreate the steps we did on CLI.
> Create all the neccesary resources on the other side, create new instances
> from the migrated volume and set a fixedIP on the neutron port to get same
> IP address.
>
> On 1/30/20 9:43 AM, Tony Pearce wrote:
>
> I want to do something similar soon and don't want to touch the db (I
> experimented with cloning the "controller" and it did not achieve any
> desired outcome).
>
> Is there a way to export an instance from Openstack in terms of something
> like a script that could re-create it on another openstack as a
> like-for-like? I guess this is assuming that the instance is linux-based
> and has cloud-init enabled.
>
>
> *Tony Pearce*   |
> *Senior Network Engineer / Infrastructure Lead **Cinglevue International
> <https://www.cinglevue.com>*
>
> Email: tony.pearce at cinglevue.com
> Web: http://www.cinglevue.com
>
> *Australia*
> 1 Walsh Loop, Joondalup, WA 6027 Australia.
>
> Direct: +61 8 6202 0036 | Main: +61 8 6202 0024
>
> Note: This email and all attachments are the sole property of Cinglevue
> International Pty Ltd. (or any of its subsidiary entities), and the
> information contained herein must be considered confidential, unless
> specified otherwise.   If you are not the intended recipient, you must not
> use or forward the information contained in these documents.   If you have
> received this message in error, please delete the email and notify the
> sender.
>
>
>
>
> On Thu, 30 Jan 2020 at 16:39, Tobias Urdin <tobias.urdin at binero.se> wrote:
>
>> We did this something similar recently, we booted all instances from
>> Cinder volume (with "Delete on terminate" set) in an old platform.
>>
>> So we added our new Ceph storage to the old platform, removed instances
>> (updated delete_on_terminate to 0 in Nova DB).
>> Then we issued a retype so cinder-volume performed a `dd` of the volume
>> from the old to the new storage.
>>
>> We then synced network/subnet/sg and started instances with same fixed IP
>> and moved floating IPs to the new platform.
>>
>> Since you only have to swap storage you should experiment with powering
>> off the instances and try doing a migrate of the volume
>> but I suspect you need to either remove the instance or do some really
>> nasty database operations.
>>
>> I would suggest always going through the API and recreate the instance
>> from the migrated volume instead of changing in the DB.
>> We had to update delete_on_terminate in DB but that was pretty trivial
>> (and I even think there is a spec that is not implemented yet that will
>> allow that from API).
>>
>> On 1/29/20 9:54 PM, Jean-Philippe Méthot wrote:
>>
>> Hi,
>>
>> We have a several hundred VMs which were built on cinder block devices as
>> root drives which use a SAN backend. Now we want to change their backend
>> from the SAN to Ceph.
>> We can shutdown the VMs but we will not destroy them. I am aware that
>> there is a cinder migrate volume command to change a volume’s backend, but
>> it requires that the volume be completely detached. Forcing a detached
>> state on
>> that volume does let the volume migration take place, but the volume’s
>> path in Nova block_device_mapping doesn’t update, for obvious reasons.
>>
>> So, I am considering forcing the volumes to a detached status in Cinder
>> and then manually updating the nova db block_device_mapping entry for each
>> volume so that the VM can boot back up afterwards.
>> However, before I start toying with the database and accidentally break
>> stuff, has anyone else ever done something similar? Got any tips or hints
>> on how best to proceed?
>>
>> Jean-Philippe Méthot
>> Openstack system administrator
>> Administrateur système Openstack
>> PlanetHoster inc.
>>
>>
>>
>>
>>
>>
>
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