Hi Melanie,
thanks for your response.
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").
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.
Thanks again!
Regards,
Eugen
Zitat von melanie witt <melwi...@gmail.com>:
On Tue, 09 Oct 2018 08:01:01 +0000, Eugen Block wrote:
So it's still unclear why nova downloaded a raw glance image to the
local filesystem during the previous attempt.
I always knew that with Ceph as backend it's recommended to use raw
images but I always assumed the "disk-format" was not more than a
display option. Well, now I know that, but this still doesn't explain
the downloaded base image.
If anyone has an idea how to reproduce such behavior or an
explanation, I'd love to hear it.
Right, in order to get the ceph CoW behavior, you must use RAW
glance image format [1]. You also need to have created the image as
'raw' before you upload to glance (qemu-img info should show the
file format as 'raw').
If you have done this, then you shouldn't see any image downloaded
to the local filesystem. Is it possible that your image did not have
file format 'raw' before you uploaded it to glance?
Cheers,
-melanie
[1] http://docs.ceph.com/docs/master/rbd/rbd-openstack
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