What is a role of the metadata service in object-based storage?

A.
Stores both objects and object IDs

B.
Maps object IDs to the file system namespace

C.
Manages a set of disks on which the user data is stored

D.
Stores data in the form of objects

Explanation:
Key components of Object-based Storage Device

The OSD system is typically composed of three key components: nodes, private network, and
storage.
The OSD system is composed of one or more nodes. A node is a server that runs the OSD
operating environment and provides services to store, retrieve, and manage data in the system.
The OSD node has two key services: metadata service and storage service. The metadata service
is responsible for generating the object ID from the contents (may also include other attributes of
data) of a file. It also maintains the mapping of the object IDs and the file system namespace. The
storage service manages a set of disks on which the user data is stored. The OSD nodes connect
to the storage via an internal network. The internal network provides node-to-node connectivity
and node-to-storage connectivity. The application server accesses the node to store and retrieve
data over an external network. In some implementations, such as CAS, the metadata service
might reside on the application server or on a separate server.
OSD typically uses low-cost and high-density disk drives to store the objects. As more capacity is
required, more disk drives can be added to the system
EMC E10-001 Student Resource Guide. Module 8: Object-based and Unified Storage