Fedora cloud image compression format

[Daniel P. Berrange]

On Thu, Mar 12, 2015 at 12:17:06PM -0400, Adam Young wrote:
> So, it looks like xz is not supported by OpenStack.
> 
> "So what" you say "OpenStack should use QCOW anyway."
> 
> Not with Ceph.  Ceph does its own COW semantics with raw, and the qcow.
> formats are not supported.  (Yes that is a regular expression dot there)

The backends used in libvirt are supposed to be agnositic to the format
of the image uploaded to glance. ie if the image in glance is stored
in qcow2, but the backend is ceph, then Nova ought to be converting the
qcow2 image to raw format on the fly, because the user shouldn't be
exposed to details of the storage backend's capability. So if ceph
has trouble if people upload qcow, then that's a bug in openstack that
needs fixing.

Adding support for uploading xz compressed raw images sounds like a
pretty good idea too, as it'd reduce the upload time. Glance could
transparantly decompress it, or leave decompression to Nova.

>   And, this is a pretty big use case.  IS there some way we can convert the
> compression to a format supported by OpenStack, either .zip or .tar.gz
> (yes, tar for some reason) or produce that as well as the xz format?

Regards,
Daniel
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