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Why are incremental backups so big?

I noticed that my 1TB backup disks seemed to have filled up very fast despite the fact that I don't really change that much in incremental backups.  Then I looked at the "Properties" of the folder.  387GB in the folder, Size on disk: 574GB!!!

Looking at individual incremental backups I see sizes (Size of file/Size on disk) of 11.0/16.1 , 4.84/8.12, 5.00/8.12 , 2.63/4.12, 8.46/16.1 , 7.72/8.12 , 1.71/2.12  ....etc.

Clearly Backerupper is allocating *LOTS* of extra space in most cases (the 1.71/2.12 case isn't too bad, but it is an anomaly).

1.  Why are these so big?

2. How can I change the backup process so that they aren't??

I should note that these were made with the free version.  I now have the paid version if that makes a difference for the answers.


  • Please send us the screenshot of "view log" page of the backup task.Please click "advanced"---"properities"---"view log".then we will see what happened? You do the folder backup right?

  • Running frequent disk defrags will cause large incrementals.

  • The backup works just fine.  It's able to be explored, etc.  It's just that it contains 4.50 GB of information and takes up 8 GB on the disk.

    ((Also, use of Flash is strongly discouraged by Firefox, and you shouldn't be requiring it to upload an image or attach a file so that I can show you what I mean.))

  • @Charlie, that's good to know, but not relevant to the question.  It might explain the 4.50GB, but not the 8.12GB.
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     @admin: Here is a screenshot and the logfile associated with that screenshot.

  • Actually, it is the 8.12 GB. maybe because there are many fragments in the disk. Please try to defragment it and then check the size of the file again.

  • edited December 2016

    I found the same problem on my other computer, and it defragmented every week.  I don't think that's the answer.  (Note: It defragged every week two days before the backup.)

    If you are talking about the disk that is accepting the backup, it hasn't been used for anything *but* backup, so it should not be fragmented!

  • How are the source and target disks formatted? What file systems?

  • Both are formatted.  Target disk is a Buffalo NAS 2TB using XFS.  Internal drive is 500GB and uses NTFS (normal for Win 10).

  • @dukeflieg Thansk for your addtional information. Please send us the whole log folder in the installations directory, we need it to find the problem. We will try to solve it ASAP. Your understanding is very appreciated.

  • edited December 2016

    I don't know XFS, but I think that has something to do with the increased disk size. On NTFS target drives the size/size on disk are about the same.

  • @admin I have attached the log directory (zipped) to this message.


  • Thanks for your log, AOMEI Technicians will try to find the problem and solve it. Your understanding is very appreciated also.

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