CLOUD STORAGE FOR CLOUD COMPUTING [ 2 ]

Cloud Storage for Cloud Computing

planning mappings of the API to several formats. Atom/Pub, JSON and Plain Text are planned for the initial release of the standard. A single URI entry point defines an OCCI interface. Interfaces expose "nouns" which have "attributes" and on which "verbs" can be performed.

Figure 1 shows how the components of an OCCI URI aligns to IaaS Resources:

Figure 2: Alignment of OCCI URI to IaaS Resources

Attributes are exposed as key-value pairs and the appropriate verbs as links. The attributes may be described as a URI. Adopting URI support affords the convenience of referencing (linking to) other interfaces including SNIA’s Cloud Data Management Interface (CDMI), for example.

The API implements CRUD operations: Create, Retrieve, Update and Delete. Each is mapped to HTTP verbs POST, GET, PUT and DELETE respectively. HEAD and OPTIONS verbs may be used to retrieve metadata and valid operations without the entity body to improve performance. All HTTP functionality can take full advantage of existing internet infrastructure including caches, proxies, gateways and other advanced functionality.

All metadata, including associations between resources is exposed via HTTP headers (e.g. the Link: header). The interface, natively expressed as Atom, executes as close as possible to the underlying Hyper Text Transfer Protocol (HTTP). In one case where the HTTP protocol did not explicitly support Atom collections, an Internet Draft (draft-johnston-http-category-header-00.txt) for a new HTTP header supporting Atom collections, has been submitted by an OCCI working group coordinator to the IETF for standardization.

OCCI provides the capabilities to govern the definition, creation, deployment, operation and retirement of infrastructures services. Using a simplified service lifecycle model, it supports the most common life cycle states offered by cloud providers. In the event providers do not support or report service life cycle states, OCCI does not mandate compliance, defining the life cycle model as only a recommendation. Cloud providers wishing to do so, can comply with the OCCI service life cycle recommendations.