Cinder/GuestAssistedSnapshotting

QEMU guest-assisted snapshotting

Goals: 1. Add snapshot support for Cinder backing stores which lack internal snapshots (NFS, Gluster, etc.)

Prerequisites:

• QEMU/libvirt live snapshot support
• QEMU guest agent installed (for quiescing)

Currently, GlusterFS + Cinder does not support snapshots. Snapshot support can be enabled by storing volume data as QCOW2 files on Cinder volumes rather than as flat raw files (as is done today), and leveraging QCOW2's snapshot functionality.

Creation of Snapshot:

1. User calls new nova API call to executed an assisted snapshot
2. Nova will quiesce guest (use existing pause functionality if guest assisted quiesce is not available)
3. Nova will execute snapshot API call in Cinder
4. Cinder creates snapshot
5. Nova resumes VM on completion of the snapshot

The snapshot can then be managed like any other Cinder snapshot.

Changes required for Cinder QCOW2 volumes:

• Cinder code to create them (per-driver code & options)
• Cinder code to translate/process them for operations like upload-to-image, backup_create, clone
• Possibly DB information tracking type (qcow2 or raw) - if needed