Object Storage Device - The OSD Standard - OSD Version 2

OSD Version 2

Work continues on a second generation of the SCSI command set, "Object-Based Storage Devices - 2" (OSD-2). The main additions are support for snapshots, collections of objects, and improved error handling.

A snapshot is a point in time copy of all the objects in a partition into a new partition. The OSD can implement a space-efficient copy using copy-on-write techniques so that the two partitions share objects that are unchanged between the snapshots, or the OSD might physically copy the data to the new partition. The standard defines clones, which are writeable, and snapshots, which are read-only.

A collection is a special kind of object that contains the identifiers of other objects. There are operations to add and delete from collections, and there are operations to get or set attributes for all the objects in a collection.

Collections are also used for error reporting. If an object becomes damaged by the occurrence of a media defect (i.e., a bad spot on the disk) or by a software error within the OSD implementation, its identifier is put into a special error collection. The higher-level storage system that uses the OSD can query this collection and take corrective action as necessary.

Read more about this topic:  Object Storage Device, The OSD Standard

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