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Data Backup 12-5
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When the filer executes the
dump
command, it displays messages showing the dif-
ferent passes of the
dump
command. This section discusses the format of the
backup data and what data is written to tape in each pass of the
dump
command.
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The backup data format is organized based on inodes. An inode for a file or a directory
contains information for tracking the files or the directorys type, time stamps, bad
blocks, and so on.
On each tape, the
dump
command creates two maps:
The first map shows which inodes are used in the directory to be dumped. The
filer uses this map to determine which files have been deleted or moved
between incremental dumps.
The second map shows which inodes have been written to the tape. The filer
uses this map to verify the accuracy of the restore operation when the backup
data is restored.
The
dump
command writes files and directories to tape by inode numbers.
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The
dump
command consists of five passes. After you enter the
dump
command,
the filer displays messages showing which pass is in progress.
In passes 1 and 2, the filer traverses directories to search for files to be backed up.
The filer backs up a file if the file meets these requirements:
The file is included in the dump path.
The file has changed since the previous backup at a lower dump level.
The file is not excluded by the exclude list specified in the
dump
command.
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If you initiate a level-1
dump
command to back up
/vol/vol0
, the filer searches for files
in
/vol/vol0
that have changed since the previous level-0 backup.
In passes 1 and 2, the filer also creates the maps described in Format of the Backup
Data.
In passes 3 and 4, the filer writes the data to tape in ascending inode order.
In pass 5, the filer writes the ACL information to tape.