SnapMirror-Synchronous (SM-S) is the NetApp ONTAP feature designed to provide zero data loss, also known as a Recovery Point Objective of zero (RPO=0). It achieves this by synchronously replicating data on a per-volume basis between a source and a destination cluster. This solution is ideal for mission-critical applications where any data loss is unacceptable, directly satisfying the government policy and regulatory requirements mentioned in the scenario. The replication is configured and managed specifically at the volume level.

A. MetroCluster: This is a comprehensive high-availability solution that provides synchronous replication, but it operates at the aggregate and SVM level, not specifically at the volume level as the question asks.

C. SnapShot Copies: These are local, point-in-time images of a volume. They do not provide data replication to a secondary site and cannot prevent data loss if the primary storage system fails.

D. SyncMirror: This technology provides synchronous mirroring at the aggregate level (RAID-level mirroring), not at the volume level. It is a component used within MetroCluster configurations.

1. NetApp Technical Report 4732: SnapMirror Synchronous Technical Overview.

Page 4, Section "SnapMirror Synchronous Overview": "SnapMirror Synchronous (SM-S) is a feature of NetApp ONTAP data management software that provides synchronous data replication at the volume level. SM-S is designed to provide a recovery point objective (RPO) of zero." This directly supports the correct answer (B).

2. NetApp Technical Report 4705: NetApp MetroCluster Solution Architecture and Design.

Page 7, Section "MetroCluster Components": "MetroCluster configurations use SyncMirror to synchronously replicate data and NVRAM between the storage controllers at each site." This confirms that MetroCluster's underlying replication mechanism is SyncMirror, which operates on aggregates, making option A less precise than B.

3. NetApp ONTAP 9 Documentation, "Data protection using SyncMirror".

Introduction: "You can use SyncMirror to create and maintain a mirrored copy of an aggregate or a traditional volume. A mirrored aggregate is called a plex." This verifies that SyncMirror operates at the aggregate level, making option D incorrect.

4. NetApp ONTAP 9 Documentation, "Overview of Snapshot copies".

Introduction: "A Snapshot copy is a read-only, point-in-time image of a volume... Snapshot copies are stored on the same volume as the original data." This confirms that Snapshot copies are local and do not provide the required disaster recovery protection, making option C incorrect.