[ceph] instance snapshot
Hello,
Im wondering about snapshotting instances using ceph rbd backend.
For example: If I have instance based on root disk I can easily snapshot it, but it actually is copy-on-write clone of a block device snapshot. Snapshots are flattened - cloned images doesn't retain a reference to the parent snapshot.
Is there any way to make openstack snapshot of VM which depends on parent image? I don't want to clone snapshot and make independent image. I just want to make quick snapshot. Nothing more.
An instance snapshot uploads an image to the Glance store; it's never a copy-on-write AFAIK. But perhaps I don't understand you. Where is RBD in your setup - is it the Glance store, the backend for ephemeral storage, or both?
I agree with Bernd Bausch, the question is not really clear. There are nova snapshots (create a new glance image --> flattened), and there are rbd snapshots (cow-clone), we use them for backups to keep instances running while rbd flattens and exports the images.