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Differential backup

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I am still confused! I run a full system backup every week and a differential backup daily (7 in all) before the next full backup. Do I need to keep all the intermediate differentials or do I only need the most recent one plus the last full one if I need to restore my data for any reason?

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Frazer, there are two aspects to your topic here.

  1. Why are you creating daily differential backups?
  2. What you need for the purpose of doing a recovery?

For the first aspect, having daily differential backups give you the ability to recovery specific data from any of the days where a backup image exists, or from several different days, hence this is a reason for keeping all the differential images for your backup version chain.

For the second aspect, then technically, you should only need to select one particular differential file to restore or recover from and ATI will automatically include the contents of the initial full backup image that that differential was based upon, ignoring the other differentials not chosen.

There have been reports of users hitting issues if unwanted differential files are deleted before doing a recovery, so for the easiest life, it is best to keep all the files to avoid such issues.  I understand that that issue should be resolved in the latest update but personally I would keep all the files to allow more choice if it is found that my chosen differential file actually has an issue or contains files which show an issue, i.e. such as malware infected etc?

Keep what you need/want - as each backup provides a point in time to recover from. If you are taking daily diffs, you can recover to that point in time, as long as you have them. You certainly can delete them (through the APP only!!!!! - use "cleanup versions" to do this), but each one you delete, removes a point in time you can recover from.  

Example where this could be a problem: 

You take a full.  Next day you take a diff.  You create an important document and that is captured in the next days diff.  You delete that important document the next day, thinking you don't need it anymore.  You take more backups and eventually get your next full so you go ahead and delete all of last weeks differentials to free up space.  However, you remember that you need some information from that document now and want to recover it.  Unfortunately, now you can't, because the backups that contained it were all deleted and it does not exist in the current full or the one that came before it.