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|Five key questions about dump (continued)|
A file is moved in the filesystem. Again, there are a few scenarios:
- The file is renamed before the directory is dumped in Pass III. When the directory is dumped in Pass III, the new name of the file will be dumped. The backup then proceeds as if the file was never renamed.
- The file is renamed after the directory is dumped in Pass III. The inode doesn't change, so dump will back up the file. However, the name of the file dumped in Pass III will not be the current filename in the filesystem. This scenario should be harmless.
- The file is moved to another directory in the same filesystem before the directory was dumped in Pass III. If the inode didn't change, then this is the same as the first scenario.
- The file is moved to another directory in the same filesystem after the directory was dumped in Pass III. If the inode didn't change, then the file will be backed up, but during a restore it would be seen in the old directory with the old name.
- The file's inode changes. The file would not be backed up, or another file may be backed up in its place (if another file has assumed this file's old inode).
If we dump
an active filesystem, will data corruption affect directories?
Most of the details outlined for files also apply to directories. The one exception is that directories are dumped in Pass III instead of Pass IV, so the time frames for changes to directories will change.
This also implies that changes to directories are less susceptible to corruption because the time that elapses between the generation of the directory list and the dump of that list is less. However, changes to files that would normally cause corresponding changes to the directory information will still create inconsistencies in the dump.
If we dump an active filesystem, will data corruption affect the entire dump or everything beyond a certain point in the dump?
Even though dump backs up files through the raw device driver, it is in effect backing up data inode by inode. This is still going through the filesystem and doing it file by file. Corrupting one file will not affect other files in the dump.
This was first published in August 2007