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Object-based storage


HCP stores objects in a repository. Each object permanently associates data HCP receives (for example, a document, an image, or a movie) with information about that data, called metadata.

An object encapsulates:

Fixed-content data — An exact digital reproduction of data as it existed before it was stored in HCP. Once it’s in the repository, this fixed-content data cannot be modified.

System metadata — System-managed properties that describe the fixed-content data (for example, its size and creation date). System metadata includes policies, such as retention and data protection level, that influence how transactions and internal processes affect the object.

Custom metadata — Optional metadata that a user or application provides to further describe the object. Custom metadata is specified as one or more annotations, where each annotation is a discrete unit of information about the object. Annotations are typically specified in XML format.

You can use custom metadata to create self-describing objects. Users and applications can use this metadata to understand and repurpose object content.

Access control list (ACL) — Optional metadata consisting of a set of grants of permissions to perform various operations on the object. Permissions can be granted to individual users or to groups of users.

ACLs are provided by users or applications and are specified in either XML or JSON format.

HCP can store multiple versions of an object, thus providing a history of how the data has changed over time. Each version is a separate object, with its own system metadata and, optionally, its own custom metadata and ACL.

HCP supports multipart uploads with the Hitachi API for Amazon S3. With a multipart upload, the data for an object is broken into multiple parts that are written to HCP independently of each other. Even though the data is written in multiple parts, the result of a multipart upload is a single object. An object for which the data is stored in multiple parts is called a multipart object.

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