[Openstack] [Nova][Glance] Nova imports flat images from base file despite ceph backend

Remo Mattei remo at italy1.com
Sat Oct 13 03:06:04 UTC 2018

Hi all
I do not have it handy now but you can verify that the image is indeed raw or qcow2 

As soon as I get home I will dig the command and pass it on. I have seen where images have extensions thinking it is raw and it is not. 


>> Il giorno 12 ott 2018, alle ore 17:17, melanie witt <melwittt at gmail.com> ha scritto:
>> On Fri, 12 Oct 2018 21:50:27 +0000, Eugen Block wrote:
>> I would consider this thread as closed. After I learned that nova
>> imports flat images if the image's disk-format is not "raw" I tested
>> some different scenarios to understand more about this topic. I still
>> couldn't explain why nova did that in the specific case as I was sure
>> the image's format was raw (the image has been deleted in the meantime
>> but I can see in the database that the image's disk-format was indeed
>> "raw").
> Thanks for sharing that info. The reason I suggested that maybe the original image wasn't created with 'raw' format (example, with 'qemu-img create -f raw ...') was because I have made that mistake before in the past. :P It is possible to upload an image to glance that is not format 'raw' and also specify to glance that it _is_ indeed 'raw' (I used the openstack CLI when I did the image upload). In that case, you will see nova download the image instead of doing ceph CoW clone.
>> But a couple of days ago I encountered the same problem. I tried to
>> upload an image from volume via Horizon dashboard (where a dropdown
>> exists to choose disk-format) and the preselected value was indeed
>> "qcow2" instead of "raw". I have no idea*why*  it was different from
>> the default "raw" but this could have happened last week, too, althoug
>> according to the database entry it should not have happened. Anyway,
>> now I know the reason why some ephemeral disks are flat, I just can't
>> tell how Horizon selects the format, but that's enough research for
>> now. If I find out more I'll report back.
> Sure, let us know if you notice anything else unusual.
> Cheers,
> -melanie
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