Format of the backup data

About this section

When the filer executes the dump command, it displays messages showing the different 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.

Backup data format

The backup data format is organized based on inodes. An inode for a file or a directory contains information for tracking the file's or the directory's 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.

Five passes of the dump command

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.

Example

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.

Copyright © 1999, Network Appliance, Inc. All rights reserved.

Part No. 210-02334
File: dump2.htm
Last updated: 02/24/99 12:17:01