Lesson 6

Date: 2/19/2014
Network File System (NFS)
Linux for Engineering and IT Applications


NFSv4 main features

  • NFS v2 and v3 are stateless protocols, but NFSv4 introduces state:
    A data structure change_info is returned by CREATE, LINK, OPEN, and REMOVE calls so the clients become aware about concurrent operations done on the NFS directories and files by the other clients. Clients can perform efficient caching and discard cache depending on the change_info.
  • Introduces file delegation:
    When a file is only being referenced by a single client, responsibility for handling all of the OPEN and CLOSE and locking operations may be delegeated to the client by the server.
  • Better file locking mechanism:
    Locks are leased by the server for certain period of time. Clients are responsible for refreshing the locks. On NFSv2 and 3, locks may become abandoned if clients come down and don't come up.
  • NFSv4 uses compound RPCs:
    Multiple related operations on a file are grouped into a single RPC call/response, thus reducing the latency of network communications.
  • A number of sophisticated security mechanisms:
    GSS-API with Kerberos and Low Infrastructure Public Key (LIPKEY) - an SSL-like model.
  • Introduces protocol support for file migration and replication.
  • Exported pseudo-file system on the server is mountable as a single common root on the client.

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