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What to do with backup set after a backup session fails


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Occasionally, one of my scheduled backup jobs will fail before completion. I am using Retrospect 6.5 on Windows 2000 Professional. All available updates have been applied to Retrospect and to Windows.


I make tape backups to an Ecrix VXA-1 SCSI tape drive. I also make "file" backups to a (big) disk file. In all cases, I use ordinary "progressive" backups that Retrospect does so well.


After such a failure, the last session on my backup set is incomplete. The question I have is, what good is the backup set now? I insist that my backup set be usable in a disaster recovery situation, where my computer has been physically destroyed, and I need to recover all data and Windows registry.


I see three possibilities:


1. I can keep writing more backup sessions on to the end of the backup set. Retrospect is so smart that it will carry on successfully.


2. No further sessions should be added to the end of the backup set. However, the backup set is still useful. It can be used to do a full disaster recovery, restore from scratch, if necessary.


3. The backup set is not reliable. Because it is in an unknown state, Retrospect may not be able to perform a disaster recovery using this backup set.


Thanks for your guidance.

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As Retrospect copies data it makes note of the file size, name, creation date etc. in the catalog file. That way everything that is contained in the set is kept on record no matter when a failure in the backup occurs.

Every time Retrospect performs a backup it looks at what is on the source disk and then what is in the entire backup set. What happened in the previous session is not all that important. What really matters are what files have already been copied to the set.

After a failure mid- backup a section of the tape was not verified against the data on the disk. However subsequent backups will compare the file entries in the catalog file against the files on disk. Any of the files that don't match will be backed up.


This is not perfect but it does pretty well. If you are really concerned you can do a media verify to check the catalog file against the data on the tapes. Either that or you can set the tape where the failure occured as "missing". Anything that was on that tape will be backed up again.


Clear as mud?



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