Application Consistent Snapshots

OpenStack snapshots of instances and volumes are at best file system consistent, but more likely only crash consistent. The main goal of this blueprint is to define a hypervisor-agnostic interface to notify applications of an impending snapshot to perform any application-specific quiesce operations prior to a filesystem freeze and snapshot as well as notification that a snapshot and thaw have completed in order for the application to perform any post-thaw operations.

This Blueprint focuses only on the narrow use-case of snapshot consistency and defines the interface necessary to ensure application consistency focusing on a KVM/QEMU implementation, as a model for all other hypervisor drivers.