Distributed Computing Environment: Difference between revisions

Revision as of 19:14, 3 February 2006

Revision as of 07:20, 2 April 2006

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There are three major components of DCE within every cell: (1) the security server (which is responsible for authentication) (2) The Cell Directory Server (CDS) (which is the respository of resources and ACLs) and (3) The Distributed Time Server which provides an accurate clock for proper functioning of the entire cell. Modern DCE implementations such as IBM's are fully capable of interoperating with Kerberos as the security server, LDAP for the CDS and the [[Network Time Protocol]] implementations for the time server.

While it is possible to implement a distributed file system using plain old DCE by defining files to the CDS and defining the appropriate ACLs on them, this is not user-friendly. DCE/DFS (Distributed Filesystem - not to be confused with the Microsoft product called [http://www.microsoft.com/windowsserver2003/technologies/storage/dfs/default.mspxDistributed DfsFile System (Microsoft)|DFS] which is NOT interoperable with DCE) is a DCE based application which provides a distributed filesystem on DCE. DCE/DFS can support replicas of a fileset (the DCE/DFS equivalent of a filesystem) on multiple DFS servers - there is one read-write copy and zero or more read only copies. Replication is supported between the read-write and the read-only copies. In addition, DCE/DFS also supports what are called "backup" filesets, which if defined for a fileset are capable of storing a version of the fileset as it was prior to the last replication.

DCE/DFS is believed to be the world's only distributed filesystem that correctly implements the full POSIX filesystem semantics - including byte range locking. DCE/DFS was sufficiently reliable and stable to be utilised by [[IBM]] to run the back-end filesystem for the 1996 Olympics web site, seamlessly and automatically distributed (and edited!) worldwide in different timezones.