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Hi all,

this still seems to be related to a thread I created last year [1].  
There was a part left which I didn't understand and couldn't  
reproduce, now a colleague seems to have created an instance where I  
can reproduce the issue.

I also found [2] and [3] referring to this, both were marked as  
invalid, but this is not resolved IMO.
I'll try to explain:

We have a volume backed instance, its base image was in raw format  
(all non-raw images were updated after I learned about the  
consequences):


# nova show output
| image                                | Attempt to boot from volume -  
no image supplied                  |
| os-extended-volumes:volumes_attached | [{"id":  
"ccca4607-3296-472b-a521-fdc3e76451a2"}]                 |


The respective volume has the following meta-data:


# cinder show output
| volume_image_metadata          | {'container_format': 'bare',  
'min_ram': '0', 'disk_format': 'raw', 'image_name':  
'###_SLES12-SP3-JeOS', 'image_id':  
'9ed2b16e-c939-42e7-9e09-4a732caf2449', 'checksum':  
'e3282f363c62194c1e4dea1bacccdda6', 'min_disk': '0', 'size':  
'1084227584'} |


I also double-checked the (exported) volume with qemu-img info that  
it's indeed a raw formatted volume.
Now when I create a nova snapshot either with Horizon or the CLI it  
results in a qcow2 image:

control:~ # nova image-create d1d4e694-3920-47e6-8338-060015c4eb71 test-image

control1:~ #  openstack image show  
7de2fd37-1124-4382-9fb4-66fde8c92676 | grep disk_format
| disk_format      | qcow2


I changed 'snapshot_image_format' from '<None>' to 'raw' in nova.conf  
on both control and compute node, although nova states to use the  
source image's format:

# If set, this decides what format is used when sending the snapshot to the
# image service.
# If not set, defaults to same type as source image.

Obviously, this doesn't work as expected, so the question is which  
component is responsible for the qcow2 format? I couldn't find related  
cinder config options, could [2] be a valid bug report after all?

Thanks for any thoughts on this!

Regards,
Eugen

[1] https://www.mail-archive.com/openstack@lists.openstack.org/msg20935.html
[2] https://bugs.launchpad.net/nova/+bug/1332558
[3] https://ask.openstack.org/en/question/65451/snapshot-defaults-to-qcow2/