On 3/26/25 10:33 AM, Martin Wege wrote: > On Tue, Feb 11, 2025 at 3:00 PM Chuck Lever <chuck.lever@xxxxxxxxxx> wrote: >> >> On 2/11/25 7:54 AM, Martin Wege wrote: >>> Is there any up to date documentation for pNFS server support in the >>> Linux 6.6 kernel? >> >> There isn't up-to-date documentation for NFSD's pNFS support. There are >> various efforts going on to improve it, but as we are swamped with other >> more pressing issues, there hasn't been good progress. >> >> pNFS block is supported, but it's not straightforward to set up. >> >> pNFS flexfiles is supported, but the implementation supports only the >> case where the DS and MDS are the same server. >> >> NFSD does not implement the other layout types. > > More questions: > 1. Clarification, please: > Which layout types are and are not supported: > LAYOUT4_NFSV4_1_FILES > LAYOUT4_OSD2_OBJECTS > LAYOUT4_BLOCK_VOLUME As I stated above, pNFS block is implemented. "Does not implement the other layout types" means the NFSV4_1_FILES and OSD2_OBJECTS layout types are not implemented. The I/O protocols that pNFS block can use include SCSI, iSCSI, and NVMe. > 2. Is Flexfiles also part of enum layouttype4, or something different? Flexfiles is a layout type. It is described in RFC 8435 https://datatracker.ietf.org/doc/html/rfc8435 NFSD's implementation is simplified and not for production use. It is useful for testing client implementations of the flexfile layout type and not much more at this time. > 3. dCache supports pNFS MetaDataServer (MDS), and NFSv3 Data Servers > (DS). Where is the spec for this? This sounds like the flexfiles layout type to me. You will have to confirm that with Tigran and his team. > And why, WHY NFSv3 DS? Why not NFSv4.1 DS= Supporting NFSv4.1 data servers is what the RFC 5661 NFSV4_1_FILES layout type already does. For more on the motivation behind flexfiles, consult RFC 8435. But generally the reasons are: - NFSv3 READ and WRITE continue to be lower latency than NFSv4 - There's still a lot of data in the world that lives on NFSv3-only servers. Serving it in place is cheaper than migrating it. -- Chuck Lever
