3dfscache - Distributed File System Implementation -...

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Distributed File System Implementation - Replication Distributed file system often provide file replication as a service to their clients. Multiple copies of selected files are maintained, with each copy on a separate file server. The major reasons: To increase reliability by having independent backups of each file. If one server goes down, or is even lost permanently, no data are lost. To allow file access to occur even if one file server is down. The motto here is: The show must go on. A server crash should not bring the entire system down until the server can be rebooted. To split the workload over multiple servers. As the system grows in size, having all the files on one server can become a performance bottleneck. By having files replicated on two or more servers, the least heavily loaded one can be used. The first two relate to improving reliability and availability; the third concerns performance. All are important.
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Replication A key issue relating to replication is transparency. To what extent are the users aware that some files are replicated? Do they play any role in the replication process, or is it handled entirely automatically? At one extreme, the users are fully aware of the replication process and can even control it. At the other, the system does everything behind their backs. In this case, we say that the system is replication transparent. Three ways replication can be done: Explicit file replication; Lazy file replication; File replication using a group; (refers to Figure 5-12)
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Explicit File Replication The programmer control the entire process. When a process makes a file, it does so on one specific server.
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3dfscache - Distributed File System Implementation -...

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