Swift has a proxy layer and a storage layer. These layers are associated with each other by way of the ring. The ring is a catalog of the objects that are being stored in the cluster and where they are being stored. This information is replicated to every storage node to improve the performance of the cluster. The proxy layer is a service that presents an API interface to end users and communicates with the storage layer on behalf of the end user. The storage layer is not generally communicated with directly.
By default, Swift uses the Swift storage engine for its storage backend. The Swift storage is a storage engine designed specifically for the Swift object storage cluster that is distributed in nature and able to be replicated. The Swift storage engine has a few subcomponents to it: the account server, the object server, and the container server.
Swift can also be backed by storage engines other than the Swift storage engine. There are a few other storage...