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For OneFS 9.3 and later, OneFS supports NFSv3, NFSv4.0, NFSv4.1, and NFSv4.2.
For OneFS 9.2 and earlier, OneFS only supports NFSv3 and NFSv4.0.
Note: NFSv4.2 just adds additional new features based on NFSv4.1, therefore, OneFS allows clients to mount NFS export with NFSv4.2, but OneFS does not implement NFSv4.2 features.
NFSv4.1 introduced several new features to the NFSv4 protocol standard, as covered in RFC-5661. These differences are covered in Section 1.8 of the RFC.
Some features are listed as required, which means that the feature must be implemented in or supported by the NFS server to claim RFC standard. Other features are listed as recommended or optional features and are supported ad hoc by the NFS server but are not required to claim RFC compliance. Starting from OneFS 9.3.0, OneFS supports NFSv4.1 and NFSv4.2 to access data by implementing all the required features defined in RFC-5661. This support excludes the Secret State Verifier (SSV) which is not implemented by any open-source Linux clients. OneFS 9.3.0 implements the session model which allows NFSv4.1 and NFSv4.2 clients to leverage trunking. Trunking is the use of multiple connections between a client and server in order to widen the I/O path. OneFS 9.3.0 supports both session trunking and client ID trunking.
Figure 1 shows the supported NFS operations in OneFS 9.3.0 and later. Both NFSv4.1 and NFSv4.2 use the existing NFSv4.0 I/O stack in OneFS. NFSv4.2 is a superset of NFSv4.1, with all new features being optional. OneFS still allows clients to mount NFS export of OneFS with NFSv4.2 and access OneFS data even OneFS does not implement any NFSv4.2 features.