AFS solves the problem of user authentification between different sites A

Afs solves the problem of user authentification

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network, AFS is a different filesystem altogether. AFS solves the problem of user authentification between different sites. A problem in sharing files between different sites around the world is that usernames and passwords are local to each site. It is possible (though perhaps unlikely) that very different users around the world might have the same user ID and login name, and even the same password. Thus AFS has to take into account the username problem. AFS also has more advanced caching features to speed up file access and access control lists (ACLs). It is in many ways superior to NFS, but whereas NFS is free software, AFS is a commercial product maintained by Transarc and is therefore not in widespread use. An improved version of AFS, called DFS has been incorporated into Digital's Distributed computing environment. 7.6.3 DCE - the distributed computing environment The Digital Equipment Corporation's Distributed Computing Environment is, in fact, as complete substitute for Sun's NFS system from RPC up. Instead of using Sun's RPC software, DCE uses software originally developed for the Apollo Domain operating system, called NCS. DCE works on top of Domain sockets. The open software foundation (OSF) has adopted DCE as its official network solution, though its on operating system NSF1 still supports NFS. One of the features of the DCE system is the concept of multiple backups of files. If one server fails, DCE allows another server to take over. This requires several servers to have disk-copies of the same files. This system is efficient on a read mostly filesystem. When a write is made to such a filesystem it must be made synchronously to disks. Maintaining these copies requires complex algorithms and a time-consuming copying overhead. DFS/DCE is also now licensed by Transarc. 8. Security: design considerations System security can mean several things. To have system security we need to protect the system from corruption and we need to protect the data on the system. There are many reasons why these need not be secure. Malicious users may try to hack into the system to destroy it. Power failure might bring the system down.
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A badly designed system may allow a user to accidentally destroy important data. A system may not be able to function any longer because one user fills up the entire disk with garbage. Although discussions of security usually concentrate on the first of these possibilities, the latter two can be equally damaging to the system in practice. One can protect against power failure by using un-interruptable power supplies (UPS). These are units which detect quickly when the power falls below a certain threshhold and switch to a battery. Although the battery does not last forever - the UPS gives a system administrator a chance to halt the system by the proper route.
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