What incremental backup images should I delete?

In this excerpt from
Answercast #5, I discuss restoring from an interrupted backup cycle and how
to save those interim increments which might contain changed data.

With backups, it’s always better to be safe than sorry.

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Data may have changed

There are two answers to this and unfortunately, the two answers are yes and no.

No, you should not delete those incrementals because they contain files that have changed between two days ago and one day ago.

Now, granted you restored specifically to a case where it’s two days ago because you didn’t want much of the change that happened between two days ago and one day ago. However, if there was a file (a data file that was important to you that was not related to the problems that you were having) that had changed in that time period, being able to have that incremental backup available would allow you to access the latest copy of that file from the backup.

You wouldn’t have to restore the entire machine. You could just go in and pick that one file or however many files that we might be talking about. So in that sense, I would absolutely save them; I would save them for awhile until you’re certain that nothing else was necessary.

Restart the backup cycle

The “yes” part of this answer is that from the backup’s point of view: you have backed up. Your machine is back at that state that it was two days ago. The backup that was taken one day ago – the incremental backup – no longer applies. So in that sense, yes, you would delete it, you would remove it. I’m going to strongly suggest that you do something else instead.

When I find myself in this kind of situation, where I’m finding myself restoring a machine to a period somewhere in the middle of a seven-day, or 30-day cycle of incremental backups, I restart the cycle.

So what I would do in your case, after having restored to something from two days ago, I would actually move (not delete, but move) the backup. I would save all of those incremental backups and then start with a brand new, fresh, full backup at that point in time.

That gives you the best of both worlds. That gives you the incremental backups that you saved prior to this problem so you can go back and get whatever files you might have missed, and it starts over a clean backup cycle from the day you restored.

Back to – Answercast #5