Network Data Management Protocol (NDMP) is a standard protocol used for backing up and restoring data on network-attached storage (NAS) devices running ONTAP. It enables backup applications to directly control data protection operations on the storage system. ONTAP supports NDMP operations for both its standard single-container volume type, FlexVol, and its scale-out, multi-container volume type, FlexGroup. This allows for efficient, direct-to-tape or direct-to-disk backups of the primary data residing in these two volume types.

A. FlexCache: A FlexCache volume is a read-only, sparse cache of an origin volume. Data protection operations, including NDMP backups, must be performed on the origin volume, not the cache itself.

B. Flash Pool: Flash Pool is not a volume type. It is an aggregate-level technology that combines SSDs and HDDs to create a hybrid storage aggregate, on which volumes are then created.

1. NetApp ONTAP 9.12.1 Documentation, "Data protection using NDMP": In the overview section, it explicitly states, "NDMP is supported on FlexVol volumes and FlexGroup volumes." This directly confirms that both C and D are correct.

2. NetApp Technical Report 4075, "FlexGroup Volumes Best Practices and Implementation Guide": In the section "Data Protection for FlexGroup Volumes," subsection "NDMP Backup," the document states, "FlexGroup volumes support NDMP-based backup and restore operations." This provides specific confirmation for FlexGroup volumes.

3. NetApp ONTAP 9.12.1 Documentation, "FlexCache volume management overview": This document clarifies the nature of FlexCache volumes, stating, "You cannot perform backup or replication operations on a FlexCache volume. You must perform these operations on the origin volume." This confirms why option A is incorrect.

4. NetApp ONTAP 9.12.1 Documentation, "Flash Pool aggregate management overview": This resource defines Flash Pool as "a type of ONTAP aggregate that is composed of both solid-state drives (SSDs) and hard disk drives (HDDs)," confirming it is an aggregate-level feature and not a volume type, making option B incorrect.