Many operating systems use the fsck program to ensure file system consistency after a system failure. The fsck program checks the consistency of a file system and reports its findings. Optionally, it repairs problems that it finds in the file system. The fsck program (or its equivalent) is still used to return consistency to many types of non-LFS partitions.
DFS employs a log mechanism and an additional system application, the DFS Salvager, to ensure the consistency of DCE LFS aggregates. A log is kept of all changes made to metadata on a DCE LFS aggregate as a result of operations such as file creation and deletion. The metadata records the structure and organization of the file system. Each DCE LFS aggregate has its own log, which physically resides on the aggregate, where it is completely transparent to users.
The DFS Salvager returns consistency to a file system when the system is restarted by replaying the log. Under normal circumstances, replaying the log returns the file system to a consistent state. However, if the Salvager detects problems in the basic structure of the aggregate, if the log mechanism is damaged, or if the physical storage medium of the aggregate is suspect, replaying the log cannot restore consistency. In these cases, a system administrator must invoke the Salvager a second time to examine and repair the structure of the aggregate.
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Differences Between the DFS Salvager and fsck
Recovering, Verifying, or Salvaging a File System