Cloned from launchpad blueprint https://blueprints.launchpad.net/nova/+spec/linked-snapshot.

Description:

The time needed from triggering snapshotting to the snapshot image available is highly depending on the size of the image generated by snapshotting. The current snapshot to clone an instance is taking too much time especially when the image size is huge (base + instance disk). To clone an instance faster, we can copy qcow2 image (instance disk) and upload it into glance as a fast-snapshot image. Each time the user launch new instances from fast-snapshot image, first check if it exists in _base folder, if not get it from glance, second check its backing file image exists in _base folder, if not get it from glance and last directly copy the fast-snapshot image to the instance folder as “disk” file. This feature can be combined with live-snapshot feature (https://blueprints.launchpad.net/nova/+spec/live-snapshot-vms)to provide fast VM clone and restoring/rollback.

Specification URL (additional information):

None