The Network Data Management Protocol (NDMP) architecture defines two logical components involved in a NAS backup operation: the NDMP Data Server, which resides on the NAS system and is responsible for reading data from (or writing data to) the underlying storage, and the NDMP Tape Server (or media server), which manages the movement of that data to or from the backup media or device. During a backup operation specifically, the Data Server component's role is to access the NAS system's storage and read the file data that needs to be protected, making this data available for transfer through the NDMP protocol to the backup infrastructure. Instructing the NAS system to start the backup (B) is a control-plane function performed by the backup server, which issues NDMP commands to initiate and coordinate the job, not a function of the Data Server component itself. Encrypting data (C) is not an inherent function of the NDMP Data Server; encryption, where implemented, is typically handled by separate security mechanisms layered onto the transfer or storage process. Scheduling and retention (D) are backup application and catalog management functions, performed by the backup server, not the NAS-resident Data Server component. Reading data from storage is correct.

Reference topic: Data Backup and Deduplication - NDMP Architecture and Components.