Network File System

See also: NFS

The filesystem in network (Network File System or NFS) is a protocol developed by Sun Microsystems which makes it possible a Ordinateur to reach file S via a network.

This Filesystem in network makes it possible to share data mainly between systems UNIX. Implementations exist for Macintosh or Microsoft Windows.

NFS is compatible with IPv6 on the majority of the systems.

NFS versions 1,2,3

Versions 1 and 2 nonprotected, are designed to function on UDP.

Version 3 is extended to deal with TCP.

At this stage the security management remains elementary and suffers from important gaps. The system is without state ( stateless ) and does not allow the recovery on incidents.

NFSv4

Inspired by AFS version 4 of the protocol marks a total rupture with the previous models. The whole of the protocol is reconsidered, and the codes are rewritten. It is about a filing system object.

Imagined to meet the needs for Internet, just NFSv4:

  • a total management of safety:
    • negotiation of the security level enters the customer and the waiter
    • simple security, support of kerberos5, certificates SPKM and possible LIPKEY
    • Chiffrement of the communications (Kerberos 5p for example)
  • increased Support of the rise in load:
    • Reduction of the traffic by grouping of requests ( compound )
    • Delegation (the customer manages the file locally)
  • Systèmes of maintenances simplified:
    • Migration: waiter NFS is migrated of the machine has towards the machine B in a transparent way for the customer
    • Réplication: the waiter has is retorted on the machine B
  • Reprise again on incidents
    • the management of the recovery on incident is integrated side customer and side waiter.
  • Compatibility:
    • NFSv4 supports Unix and now Ms-Windows
  • Support of several protocols of transport (TCP, RDMA)

However these improvements of NFSv4 make NFSv4 incompatible with NFSv3. In particular, the recovery on incident and the delegation imply that NFSv4 is a waiter in state ( statefull ), noncompatible with the preceding versions. Moreover, NFSv4 is not designed to support UDP.

For all these reasons it is highly preferable to use NFSv4 rather than NFSv3, insofar as a total migration is possible.

NFSv4.1

Version 4.1 of NFS is with the state of RFC. This version resulting from NFSv4 is inspired by PNFS and GLOSS, as well as protocols Internet such as HTTP. It benefits from the design object of the protocol. The concept of Geometry of file and that of segments are from now on abstract: they can be paralleled or use multiple ways towards the data. The use of primarily hollow file is optimized. The transport of data is also abstract, and is now independent not only of TCP but also of IP. The concept of session makes its appearance.

  • Delegation by repertories

  • Sessions: the session of a user can be stopped and restored.
    • Simplification of the support of the Failover.
    • Abstraction of the protocols of transport, independence of IP and TCP.
  • Abstraction of the geometry of files:
    • Parallelization of the access to the files (Stripping)

Although the RFC of versions 4.1 are not stabilized, the implementation of the protocol already began on the majority from the Unix solutions.

References

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