Open Stack

Hi Zheng, comments inline...

On 11/09/2015 02:04 AM, Zhenyu Zheng wrote:
> Hi All,
>
> Currently, we have strong demands about "rebuilding"(or actions like
> rebuilding) volume-backed instances. As in production deployment, volume
> backed instance is widely used. Users have the demands of performing the
> rebuild(recovery) action

Rebuild definitely does not equal recovery in Nova. It is *not* a 
data-safe operation and was never intended as such. More below...

 > for root device while maintain instance UUID
> sorts of information, many users also wants to keep the volume uuid
> unchanged.

I can kind of see the argument for maintaining volume UUID, instance 
UUID and IP addresses for purposes of not breaking orchestration tooling 
or scripts that refer to the UUID. It's not cloudy, but for "pet" VMs, 
it's a pretty common request.

> Nova side doesn't support using Rebuild API directly for volume backed
> instances (the volume will not change).

The rebuild API "starts over from scratch" and therefore doesn't make 
sense for volume-backed instances (because there is no starting over 
from scratch since all data on the root volume is saved to the volume).

 > And Nova side also doesn't
> support detaching root device, that means we cannot performing volume
> backup/restore from cinder side, because those actions needs the volume
> in "available" status.

Couldn't you just snapshot the instance? That is the recommended way to 
perform a "backup" operation.

Changing the operating system (mentioned in your followup post response 
to Clint) isn't a "restore" operation that I've ever heard of. Are you 
actually referring to a *rescue* API operation here?

http://developer.openstack.org/api-ref-compute-v2.1.html#rescue

Best,
-jay

> Now there are couple of patches proposed in nova trying to fix this problem:
> [1] https://review.openstack.org/#/c/201458/
> [2] https://review.openstack.org/#/c/221732/
> [3] https://review.openstack.org/#/c/223887/
>
> [1] and [2] are trying to expose the API of detaching root devices, [3]
> is trying to fix it in the current Rebuild API. But yet none of them got
> much attention.
>
> As we now have strong demand on performing the "rebuilding" action for
> volume-backed instances, and yet there is not any clear information
> about  it. I wonder is there any plans of how to support it in Nova and
> Cinder?
>
> Yours,
>
> Zheng
>
>
> __________________________________________________________________________
> OpenStack Development Mailing List (not for usage questions)
> Unsubscribe: OpenStack-dev-request at lists.openstack.org?subject:unsubscribe
> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
>