** Also affects: cinder Importance: Undecided Status: New -- You received this bug notification because you are a member of Yahoo! Engineering Team, which is subscribed to Glance. https://bugs.launchpad.net/bugs/1818851
Title: Snapshots of volume backed instances default to qcow2 Status in Cinder: New Status in Glance: New Bug description: This report applies to a production Ocata cloud and also to a Rocky lab environment. I'm not entirely sure which component is responsible exactly but the inconsistency is strongly related to glance. This report results from a mailing list thread I started in October 2018 [1], I only could put the pieces together step by step as some of the behavior was not reproducible, so this took a while, and my conclusion is summed up in [2]. I'll recap here: The backend for nova, cinder and glance is ceph. 1. Creating an instance from a (regular) glance image with 'disk_format = qcow2' results in a "flat" nova instance with no parent data. Although a snapshot seems to create a "raw" image it's actually "qcow2", resulting in more flat images if instances are launched from this new image. 2. Creating a snapshot of a volume based nova instance (raw format) unexpectedly results in a glance image with 'disk_format = qcow2'. But launching a new instance from that snapshot does *not* result in a flat image as I would have expected because of 1. Instead the new instance is a cow-clone of the original volume, which in fact is expected because of the ceph backend. So the workflow seems fine, but I find it very confusing (obviously) that the volume based snapshot is declared as a qcow2 image, that doesn't seem right. Steps to reproduce (part I): 1. Create qcow2 image. 2. Launch instance from qcow2 image. 3. Instance has no parent data, it's a flat rbd image without 'parent data'. Steps to reproduce (part II): 1. Create raw image. 2. Launch volume backed instance from raw image. 3. Create snapshot of instance, resulting in a glance image with 'disk_format = qcow2'. 4. Launch instance from that image, results in a new copy-on-write clone (volume). Expected result: Snapshot of a volume backed instance should also have 'disk_format=raw'. The consequences of the image property 'disk_format' should always be the same, no matter how the image was created. Actual result: Depending on the image creation the same property 'disk_format' has different effects on the ceph backend and the resulting usability. [1] https://www.mail-archive.com/openstack@lists.openstack.org/msg20935.html [2] http://lists.openstack.org/pipermail/openstack-discuss/2019-March/003383.html To manage notifications about this bug go to: https://bugs.launchpad.net/cinder/+bug/1818851/+subscriptions -- Mailing list: https://launchpad.net/~yahoo-eng-team Post to : yahoo-eng-team@lists.launchpad.net Unsubscribe : https://launchpad.net/~yahoo-eng-team More help : https://help.launchpad.net/ListHelp