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Cinder System Architecture
==========================

The Cinder Block Storage Service is intended to be ran on one or more nodes.

Cinder uses a sql-based central database that is shared by all Cinder services
in the system. The amount and depth of the data fits into a sql database quite
well. For small deployments this seems like an optimal solution. For larger
deployments, and especially if security is a concern, cinder will be moving
towards multiple data stores with some kind of aggregation system.

Components
----------

Below you will find a brief explanation of the different components.

::

                                                  /- ( LDAP )
                              [ Auth Manager ] ---
                                     |            \- ( DB )
                                     |
                                     |
                    cinderclient     |
                   /             \   |                   /- [ scheduler ] -- [ volume ] -- ( iSCSI )
 [ Web Dashboard ]-               -[ api ] -- < AMQP > --
                   \             /   |                   \- [ backup ]
                    novaclient       |
                                     |
                                     |
                                     |
                                  < REST >


* DB: sql database for data storage. Used by all components (LINKS NOT SHOWN).
* Web Dashboard: potential external component that talks to the api.
* api: component that receives http requests, converts commands and
  communicates with other components via the queue or http.
* Auth Manager: component responsible for users/projects/and roles. Can backend
  to DB or LDAP. This is not a separate binary, but rather a python class that
  is used by most components in the system.
* scheduler: decides which host gets each volume.
* volume: manages dynamically attachable block devices.
* backup: manages backups of block storage devices.
