Hello Nova developers,

Cinder is working on a feature that will allow it to compress volumes uploaded to Glance [0,1].  We are proposing a new container_format for Glance named 'compressed' [2].

The idea is that a consumer of a 'compressed' image would read the file to determine the kind of compression and take appropriate action (either successfully decompress to find a payload that matches the image's disk_format, or fail with 'unsupported container_format').

Our preliminary testing with a raw image with container_format == compressed, disk_format == raw is that Nova boots a VM from the image but the VM appears to be unusable.  Nova seems taking it as a real RAW image as disk_format indicates.

So we want to open a discussion about handling this.

Thanks!

[0] cinder spec patch   https://review.opendev.org/#/c/652275/

[1] cinder code implementation https://review.opendev.org/#/c/668825

[2] glance spec patch     https://review.opendev.org/#/c/670454/