Here is a short summary of new features. For a complete discussion of these features, see the documentation provided by the NFSv4 Working Group.
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NFS Versions 2 and 3 are stateless protocols, but NFS Version 4 introduces state. An NFS Version 4 client uses state to notify an NFS Version 4 server of its intentions on a file: locking, reading, writing, and so on. An NFS Version 4 server can return information to a client about what other clients have intentions on a file to allow a client to cache file data more aggressively via delegation. To help keep state consistent, more sophisticated client and server reboot recovery mechanisms are built in to the NFS Version 4 protocol.
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NFS Version 4 introduces support for byte-range locking and share reservation. Locking in NFS Version 4 is lease-based, so an NFS Version 4 client must maintain contact with an NFS Version 4 server to continue extending its open and lock leases.
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NFS Version 4 introduces file delegation. An NFS Version 4 server can allow an NFS Version 4 client to access and modify a file in it's own cache without sending any network requests to the server, until the server indicates via a callback that another client wishes to access a file. This reduces the amount of traffic between NFS Version 4 client and server considerably in cases where no other clients wish to access a set of files concurrently.
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NFS Version 4 uses compound RPCs. An NFS Version 4 client can combine several traditional NFS operations (LOOKUP, OPEN, and READ, for example) into a single RPC request to carry out a complex operation in one network round trip.
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NFS Version 4 specifies a number of sophisticated security mechanisms, and mandates their implementation by all conforming clients. These mechanisms include Kerberos 5 and SPKM3, in addition to traditional AUTH_SYS security. A new API is provided to allow easy addition of new security mechanisms in the future.
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NFS Version 4 standardizes the use and interpretation of ACLs across Posix and Windows environments. It also supports named attributes. User and group information is stored in the form of strings, not as numeric values. ACLs, user names, group names, and named attributes are stored with UTF-8 encoding.
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NFS Version 4 combines the disparate NFS protocols (stat, NLM, mount, ACL, and NFS) into a single protocol specification to allow better compatibility with network firewalls.
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NFS Version 4 introduces protocol support for file migration and replication.
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NFS Version 4 requires support of RPC over streaming network transport protocols such as TCP. Although many NFS Version 4 clients continue to support RPC via datagrams, this support may be phased out over time in favor of more reliable stream transport protocols.
Answered by
Yuvee
at
8:13 PM on December 18, 2008
