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Cinder has, and probably will, continue to resist operations that are only
added so that some other operation can be done while 'keeping the volume
UID'. It is not a cloud mentality, and it leads to increased code
complexity and in several cases risk of data loss within cinder.

On 9 November 2015 at 10:21, Zhenyu Zheng <zhengzhenyulixi at gmail.com> wrote:

> Hi,
>
> Thanks for the reply, for some scenario, launching an new instance is
> easier. But for production deployment, an instance may contain a large
> number of data such as keypairs, metadata, bdm etc. and it may have
> multiple internet interfaces that are connected to multiple networks. That
> is to say, for operations like recovery, change/update operating system, to
> build an new instance is a lot more "expensive" than rebuild it. And one
> instance may have some volumes that are marked as delete_on_terminate =
> True, if that is the situation, build an new instance will not save the
> user data in user volume, but rebuild can protect them.
>
> So, I think this is a quite reasonable demand for OpenStack.
>
>
>
> On Mon, Nov 9, 2015 at 3:28 PM, Clint Byrum <clint at fewbar.com> wrote:
>
>> Excerpts from Zhenyu Zheng's message of 2015-11-08 23:04:59 -0800:
>> > 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 for root device while maintain instance UUID
>> sorts
>> > of information, many users also wants to keep the volume uuid unchanged.
>> >
>> > Nova side doesn't support using Rebuild API directly for volume backed
>> > instances (the volume will not change). 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.
>> >
>> > 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?
>> >
>>
>> This seems entirely misguided by the users.
>>
>> Why not just boot a new instance on a new volume with the same image?
>> Names can be the same.. UUID's should never be anything except a physical
>> handle.
>>
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>
>
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-- 
-- 
Duncan Thomas
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