On 2020-05-26 10:29:17 +0200 (+0200), Thomas Goirand wrote: [...] > Able to extract the .raw file from a tar.xz? I don't think so. If > it can, please provide the command line to do that, but as much as > I know, it's currently not possible. I'd love to be wrong here... [...] It *can* be done with Glance's "tasks" API: https://docs.openstack.org/glance/latest/admin/tasks.html However that would require every deployment you're using the files with to have that custom task defined by the Glance administrator. There are some common tasks which perform image conversion, say between raw and qcow2, but in general that API was a terrible idea because any time you expose a Turing-complete interface as an API you can kiss cross-deployment interoperability guarantees goodbye. > Now, while what you're saying about RBD may be right, this still > doesn't help OpenStack users, as the images must be uploaded > through Glance, and sparse files aren't understood by > glanceclient. [...] Also don't forget that Glance is only part of the story there when it comes to image transfer and storage. Compute nodes need a copy of anything they're going to boot (unless you're configured to do boot-from-volume using copy-on-write with Cinder and Glance sharing the same backend store), so the larger the logical image size, the longer it takes to retrieve from Glance or the backend and the more space it potentially takes in the local image cache. I have seen image uploads cripple storage networks when lots of compute nodes try to fetch copies of a new image into their cache all at once. The bigger the image, the more pronounced the impact from that thundering herd. -- Jeremy Stanley
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