The Major Differences Between NFS Versions 2 and 3


This articles discusses some major differences between Network File System (NFS) version 2 and version 3.

NFS Version 2 is documented in RFC 1094 and was published in March 1989. NFS Version 3 is documented in RFC 1813 and was published in June 1995.

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NOTE: Services for Unix 2.0 supports both NFS versions 2 and 3.

The major differences between the NFS versions 2 and 3 are:
  • Version 2 of the NFS protocol limited file offsets to a 32-bit quantity, which limited the size of files accessible by clients to 4.2 GB. For users who regularly gain access to larger files, this was a severe limitation. NFS version 3 extended the file offsets and a number of other fields to 64-bits.
  • NFS Version 2 limited the data transfer size to 8 KB. No single read or write request could exceed 8 KB. This limits performance on high-bandwidth networks because it artificially increases the number of NFS requests to transfer a given amount of data. NFS version 3 removed that limitation and allows the client and server to negotiate a maximum transfer size.
  • Version 2 NFS servers must commit data written by a client to stable storage (a disk or NVRAM) before responding affirmatively to the client.
  • NFS version 3 provides a new COMMIT operation that allows a client to perform unstable writes to a server followed by a COMMIT request. The server is required to verify that client data is on stable storage only when it receives the COMMIT operation. A mechanism is provided that allows the client to detect server loss of uncommitted data and recover.

ID članka: 233492 - posljednja izmjena: 31. lis 2006. - verzija: 1

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