Essex-golden-image

Golden Image Flow

An openstack user should be able to create images that work in their cloud with minimal knowledge of the implementation details of the cloud (hypervisor). This blueprint addresses supporting the creation of an image that supports of a wide variety of hypervisors.

Questions that a user has to decide:

• how to create an image that the user can upload to the cloud
• what format their image should be to support multiple clouds (golden format)

Questions for the nova hypervisor drivers:

• can nova either use the golden format or convert it to the preferred runtime format
• can nova create snapshot of running images that allows re-launching
• can a user (easily) convert the snapshot format back to original (golden) format

Story:

• user uploads raw[.gz?] image to glance (optionally support internal format although we want to encourage raw as the standard) in cloud.
• Nova-compute can convert to an optimized runtime format (if needed) at runtime.
• The user snapshots, which uploads the snapshot to glance - in either raw or internal format.
• The user can launch multiple copies of the snapshot.
• The user can download the snapshot (which is converted to raw on client)

Implementation

Assumptions:

• raw images are supported in all hypervisors
• kvm driver would create a qcow2 cow image backed to the raw image
• rax uses xs driver and would use VHD runtime images (raw converted to vhd?)
• citrix uses xs driver but prefers images ___
• lxc driver uses ?
• vmware driver uses ?

Questions

• Does since raw images are large, should we use gzipped raw images?
• glance client would need work with qemu-img to convert back to raw?
• Does our golden image support the disk-management changes (specifying root and ephemeral space independently in flavors)?

Task:

• document how to create golden images / provide examples to users
• ensure hypervisors support golden image
• ensure integration test coverage for flow

Post Essex

• user uploads raw[.gz?] image to glance (optionally support internal format although we want to encourage raw as the standard) in cloud
• Post ingestion glance converts to an optimized runtime format.
• The user snapshots, which uploads the snapshot to glance - in either raw or internal format.
• The user can launch multiple copies of the snapshot.
• The user can download the snapshot (which was converted to raw on service)