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How do I create an incremental Volume Group backup using "stbackup" command?

How do I create an incremental Volume Group backup using "stbackup" command?

Can you tell me (and give an example) of what the incremental option (-l) is all about for stbackup?
What does it mean to do an incremental backup of a volume group xxx to level 2?


ANSWER

First, you will find documentation on incremental backups with the "stbackup" and "strestore" commands in the SBAdmin Commands Reference Guide. If you're using the GUI or Web Interface, you may get good information using QuickHelp on the incremental level field.

General guidelines:
- Leave this blank if not using incremental backups
- Set to 0 to perform a full incremental backup (same as blank except we now store the incremental filelist and timestamp)
- Set to 1 or higher to include only files which have changed since the last PRIOR level backup.

For example, perform a level 0 to get all files, do a level 1 to get all files changed since the last level 0. You can then do a level 4 to backup all files changed since the last level 1 (since there is no 2 or 3), and do a level 4 again to again backup the files that changed since the level 1. Doing another level 1 negates the level 4's and doing another level 0 negates all subsequent levels (1 and 4), etc.

When restoring, always start with level 0, then apply each subsequent level if it is more recent than the last prior level. For instance, if a level 1 is older than your level 0, you don't need it. If your last level 4 is older than your level 1, you don't need it.

Volume Group Incrementals:
The incremental level will be applied to each filesystem or logical volume included in the backup as if you were doing a separate incremental backup of each. You can later do another incremental backup of the same volume group, or you can do an incremental backup of only a filesystem within the volume group.

For example, If you do an incremental level 0 backup or a volume group "uservg", you can then do an incremental level 1 of one or more of the filesystems within "uservg" independently. This saves having to do an incremental level 0 backup of each filesystem before doing subsequent incremental levels of each.

Raw logical volume backups are treated like filesystems when backed up incrementally, except that the entire logical volume will be backed up if it was written to since the last pror-level backup. It is not possible to backup only the changed data within a logical volume as it is known only as a single file.