This reviews the IETF Parallel Network File System (pNFS), an extension to NFS that separates file metadata from data storage. Specifically, "RFC 8435" introduces the initial flexible file layout type, enabling pNFS to utilize existing protocols and storage devices with limited metadata server interaction, incorporating client-side mirroring for data replication. Then we review, "Parallel NFS (pNFS) Flexible File Layout Version 2," details an update to this layout, enhancing data protection with additional methods like the Mojette algorithm, and refining the management of tightly and loosely coupled storage device models, including how client I/O errors and layout usage statistics are reported and managed. Both sources discuss the mechanisms for recalling layouts, client fencing, and the security considerations inherent in these distributed file system architectures.

Sources: https://www.ietf.org/archive/id/draft-ietf-nfsv4-layoutwcc-02.html - Add LAYOUT_WCC to NFSv4.2's Flex File Layout Type

https://www.ietf.org/archive/id/draft-haynes-nfsv4-flexfiles-v2-00.html - Parallel NFS (pNFS) Flexible File Layout Version 2

https://datatracker.ietf.org/doc/rfc8435/ - Parallel NFS (pNFS) Flexible File Layout

RFC 8435