Does defragmentation affect file ("My Data") incremental backups?

Discussion in 'Acronis True Image Product Line' started by randman, Apr 14, 2007.

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  1. randman

    randman Registered Member

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    I apologize if this has been discussed before, but I spent quite a bit of time trying to find this answer to no avail.

    I understand that if a hard drive is defragged, an incremental image backup taken after the defrag will be very large.

    My question is: if I take a file backup ("My Data" backup) instead of a partition/disk image backup ("My Computer" backup), does file backup only backup the files that were changed since the last backup, so it is not affected by defragmentation?

    For example, if I take a Full file ("My Data") backup, then I change one and only one file, then do a defragmentation, will the next incremental file backup only backup one file?

    I like keeping my disks defragged. I was wondering whether I need a more traditional (i.e. non-imaging) backup program to handle my "Documents and Settings" folder, and use ATI just for my Windows and Program Files partitions. But, if ATI can behave like a traditional (non-imaging) utility for my data files, then it has the best of both worlds: imaging, and traditional file backup. This distinction is discussed in the ATI manual, but it's just not clear to me whether or not defragmentation affects file (non-image) backups.

    Thanks.
     
  2. jmk94903

    jmk94903 Registered Member

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    Since you are doing a file backup, the defragging should make no difference at all in the size of the backup.

    It's certainly easy to cofirm this. Do a backup. Defrag and repeat the backup. It should be almost exactly the same size as the previous differential.
     
  3. mmaterie

    mmaterie Registered Member

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    Defrag won't impact what your backup program decides to store for incrementals. The only change that occurs on the disk during a defrag is the "pointers" to the file's previous locations is updated to the files new location(s). That occurs in the MFT record for the file on NTFS or the FAT table for FAT volumes.
     
  4. nb47

    nb47 Registered Member

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    Well ,I always defrag right before a backup on my C: drive but I've read on here you shouldn't defrag the E:/ (external HD) so I don't touch that one.
     
  5. jmk94903

    jmk94903 Registered Member

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    If your system fully supports the external drive, you can defrag it safely. How do you know? Well, if you defrag the external drive and the backups are no longer validated, then you don't have full support.

    It's a catch 22. Since you won't be restoring on a regular basis, the speed of the external drive isn't a big deal. Therefore, not defragging is a practical decision.

    Personally, my external USB drive defrags without a problem.
     
  6. randman

    randman Registered Member

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    Thanks. I just upgraded to ATI 10.0, and will try this test.
     
  7. randman

    randman Registered Member

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    With ATI 10.0, I determined that doing a disk defragmentation has no effect on file ("My Data") backups (as expected, but I wanted to confirm). Here's what I did to prove this:

    1. I did a "My Data" full backup of E:\Documents and Settings.

    2. Without making any changes to E:\Documents and Settings, I did a "My Data" (i.e. file) differential backup. The differential backup had a size of 748KB. I assume this 748KB is mainly overhead since no files were changed.

    3. I copied a file with size 33,607KB to E:\Documents and Settings.

    4. I did another file differential backup. The differential backup had a size of 34,276KB.

    5. I defragged my E: drive.

    6. I did another file differential backup. The differential backup had a size of 34,277KB, which is basically the same size as the differential backup taken before I defragged my drive.

    To summarize, "My Data" (i.e. file) differential backups are not affected by disk defragmentation. This is what I suspected all along, but the Acronis documentation and online Acronis FAQ do not explicitly state this. The Acronis documentation states that defragmentation will affect the size of differential backups. It should be changed to say that this is only true for disk or partition (i.e. image) differential (and I assume incremental) backups. It should explicitly state that "My Data" backups are NOT sector backups and behave more like traditional non-imaging backup software. It would also be useful if the Acronis FAQ mentioned this.

    Thanks to all.
     
  8. Acronis Support

    Acronis Support Acronis Support Staff

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    Hello randman and everyone interested,

    Thank you for choosing Acronis Disk Backup Software.

    Would like to clarify the situation with defragmentation and using Acronis True Image to create backup archives.

    Please note that defragmentation may affect the size of the incremental/differential image archive (disk/partition image) created with Acronis True Image. This is because Acronis True Image operates on a sector level to create disk/partition image. When you defragment the drive the data is moved from one sector to another. Acronis True Image will see that the data on the sector has changed and will include the content of the sector to the image archive.

    File-based backup (backup of separate files/folders) operates on a file-system level and back up only the data, along with the folder tree. Therefore, defragmentation does not affect the size of the incremental/differential file-based backup.

    Thank you.
    --
    Aleksandr Isakov
     
  9. randman

    randman Registered Member

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    Thanks. That was the conclusion I reached from my testing. May I suggest that what you just mentioned be added to a future version of the user's guide and to the FAQ, just to make it explicitly clear that defragmentation does not afffect file backup? Currently the 10.0 version of the documentation says:

    "An incremental or differential backup created after a disk is defragmented might be considerably larger than usual. This is because the defragmentation program changes file locations on disk and the backups reflect these changes. Therefore, it is recommended that you re-create a full backup after disk defragmentation."

    The paragraph above does not explicitly state that it is only relevant for partition/image backups. It would be good to clarify this in a future version of the user's guide and in the FAQ.

    Thanks!
     
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