pNFS – Parallel NFS is a new standard part of NFS version 4.1. A NetApp document says: NFSv4.1 (RFC 5662) is a minor release of NFSv4. NFSv4.1 does not modify any NFSv4 features and functionalities—it simply enhances what is already in place. With traditional NFS versions 3, 4, and 4.1, metadata and data are shared on the same I/O path. With pNFS, for the first time, there is an NFS feature that handles metadata and data on different I/O paths.
A metadata server handles all metadata activities from the client while the data servers provide a direct path for data access. pNFS has three different implementations: files, blocks, and objects. NetApp supports only file implementation at this time. The client communicates with the metadata server over NFSv4.1 while access to the data servers is through files, blocks, or objects. Every storage vendor has a different way of implementing pNFS in their stack, and NetApp supports pNFS only in clustered Data ONTAP at this time. There is no Data ONTAP 7G/7-Mode support for pNFS.
