The Image Registry Service is a part of Cyclades. It is implemented as a very thin layer on top of Pithos; every Image on the Image Service is a file on Pithos, with special metadata which are stored on Cyclades. At the frontend, Cyclades implement the OpenStack Glance API; at the backend it queries an existing Pithos backend. In the current implementation the service runs the Image Service and Pithos on a single, unified backend: users may synchronize their Images, using the Pithos clients, then register them with Cyclades, with zero data movement. Then spawn new VMs from those Images with Cyclades.
Let’s see below:
The figure shows a sailor bundling his physical machine with the snf-image-creator tool, uploading the file to Pithos, registering the file as a new Image, and then spawning two new VMs with Cyclades from this Image.