Which technology is utilized for more efficient transfers when the datastores of published and subscribed libraries are on the same storage array?

The correct answer is VAAI (vStorage APIs for Array Integration). This technology enhances the efficiency of data transfers when the datastores of published and subscribed libraries are located on the same storage array. VAAI allows certain operations to be offloaded to the storage array itself, which can significantly reduce the overhead on the ESXi hosts and improve the performance of storage-related tasks.

When VAAI is used, operations like cloning, moving, and creating snapshots can be processed directly by the storage array, rather than needing to fetch and process data over the network. This offloading not only speeds up these processes but also reduces the load on the ESXi host, allowing it to allocate resources more effectively for other tasks.

In contrast, the other technologies listed serve different purposes: iSCSI is a protocol used for connecting storage devices over IP networks, NFS is a network file system protocol that allows for file sharing over a network, and RAID (Redundant Array of Independent Disks) is primarily concerned with data redundancy and performance improvement through disk configurations rather than specific integration with virtualization management operations. Thus, these options do not offer the same efficiencies for datastore transfers as VAAI when dealing with operations on the same storage array.