Volume snapshots are implemented using the GPFS file clone feature. Whenever a new snapshot is created, the snapshot file is efficiently created as a read-only clone parent of the volume, and the volume file uses copy-on-write optimization strategy to minimize data movement.
Similarly when a new volume is created from a
snapshot or from an existing volume, the same approach
is taken. The same approach is also used when a new
volume is created from a Glance image, if the source
image is in raw format, and
gpfs_images_share_mode is set
to copy_on_write.
