Object storage

Ephemeral backing storage for compute instances is provided by the Nova service. This storage is referred to as ephemeral because its life cycle coterminates with the life cycle of the compute instance. That is, when an instance is terminated, the ephemeral storage associated with the instance is deleted from the compute host on which it resided. The first kind of persistent storage provided in the OpenStack system was object storage, based on the S3 service available in the Amazon Web Service environment.

Object Storage is provided by the Swift service in OpenStack. Just as Nova provides an EC2- compatible compute API, Swift provides an S3-compatible object storage API. Applications which are written to run on the Amazon EC2 service and read and write their persistent data to the S3 Object Storage service do not need to be rewritten to run on an OpenStack system.

A number of third-party applications provide an S3 or Swift-compatible API, and they may be substituted for Swift in a typical OpenStack deployment. These include open source object stores, such as Gluster or Ceph, or proprietary ones, such as Scality or Cloudian. The Swift service is broken down into a few components, and third-party applications may use the Proxy component of Swift for API services and implement only a backend, or may replace the Swift service entirely. All OpenStack-compatible object stores will consume the tenant model of OpenStack and accept Keystone tokens for authentication.