How do incremental file backups work? Archive bit?

Discussion in 'Acronis True Image Product Line' started by networkROI, Oct 4, 2007.

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  1. networkROI

    networkROI Registered Member

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    I am trying to work out a rota to backup a server using ATI 9.1

    What I want is a combination of a Disk backup and a File backup.

    Every night I want to run a full disk-based backup of the whole server to an external USB drive. This will be rotated with a second USB drive and will keep one full backup.

    Every 1st day of the month I want to run a full file-based backup of a key data folder within the server. Following that backup I want to run an incremental backup of the same data folder each day for the rest of the month. This will be to a NAS device on the local network.

    The idea behind this is that there will always be an off-site backup in case of a fire and also the ability to get a decent history of backups for the key data area running back up to a year.

    The reason I am posting is that I know with traditional backup programs the 'archive bit' plays a big part in incremental (or differential) backups so that the program can work out what files have changed since the last backup.

    I am wondering if the full disk-based backup will screw-up the file-based incremental backup?

    If some ATI techie can tell me the basis on which incremental (and differential) backups determine whether or not a file has changed I will be able to work out the best strategy.

    Thanks
    Ian
     
  2. seekforever

    seekforever Registered Member

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    Ti does not use the archive bit for a Files and Folders (FF)backup. Just how it determines the files for a FF backup, I can't say. In an image backup, it compares in-use sector maps.

    When TI does an incremental or differential it looks at the last backup or full archive of the same type to decide what has changed. So an image backup will look at the "previous" image and a FF backup will look at the appropriate previous FF. There should not be any problem with the image confusing the FF or vice-versa.
     
  3. networkROI

    networkROI Registered Member

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    That sounds great. I did a little testing and when I altered the archive bit it did trigger to backup that file but it did not alter the archive bit. Weird. I gues the archive bit changing was enough to make the file itself change and require backing up.

    Would be great to hear from the dev team exactly how the incrementals and differentials work for file-based backup.

    Thanks
    Ian
     
  4. seekforever

    seekforever Registered Member

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    A change is a change, even if it is only the archive bit!

    You may or may not hear details about how TI does things; they don't like to say exactly how various things work. Having said that, IIRC, I think there might be a post on the forum from within the last year with some details - my personal RAM is not as good as my computer's though :D . You could try searching the forum.
     
  5. Pinchas

    Pinchas Registered Member

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    when atih starts creating incremental backup does it check the previous incremental backup only, or the initial full backup and the last incremental backup to determine cahnges?
     
  6. seekforever

    seekforever Registered Member

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    The quick answer is that I don't know how TI works internally.

    However, the incremental being created captures all of the changes since the last incremental and for that reason I would say that the last incremental has sufficient information in it to facilitate the creation.

    IMO, if it has to go back further, it would make more sense to say it had to go back to the full and the complete chain of incrementals rather than just the full and last incremental.

    In the case of the differential, it always goes back to the full only.
     
  7. Acronis Support

    Acronis Support Acronis Support Staff

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    Hello Pinchas,

    Thank you for choosing Acronis Disk Backup Software.

    Actually, when Acronis True Image creates an incremental backup, it compares the data to be backed up with the data as it would be if the archive was restored up to the last incremental backup.

    If you have any further questions concerning Acronis software, please feel free to submit a request for technical support or post any of them on this forum. We will certainly try to help you in resolving any issues.

    Thank you.
    --
    Marat Setdikov
     
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