Backups: full, incremental, differential

Discussion in 'Acronis True Image Product Line' started by dylanfan, Jun 8, 2006.

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  1. dylanfan

    dylanfan Registered Member

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    Hi everybody;

    I understand the meaning of "full backup", but I can't really understand the difference between "incremental backup" and "differential backup"...

    Can anyone help?

    Cheers
     
  2. satchmo

    satchmo Registered Member

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    I will try explaining it with a couple of examples.

    On Monday I take a full backup. It represents my files or sectors or whatever you are tracking. Let's say the contents of the full backup equal ABC.

    During the week you work on the machine and the contents have now changed. The contents now look like ABCDEF. Then when you take the differential the differential file would contain DEF and together with the full backup equal the state at the time of the differential backup.

    Incremental backups are just chains of differentials using the state of the previous differential as the basis of comparison and not the full backup up. An example might make this more clear.

    Monday Take a full backup = ABC

    On Tuesday the current state equals ABCD, so the incremental you take on Tuesday contains D. I can reconstruct the state by adding the incremental and the fule backup.

    On Wednesday the current state equals ABCDE, so the incremntal you take contains E, since it is relative to the sate on Tuesday. I can reconstruct the state by adding the Wednesday's incremental with Tuesday's incremental with the full backup.

    You can see that both differentials and incrementals are dependent. In the case of incrementals, if you lose the Tuesday incremental, then everything after that is meaningless since they are dependent upon it.

    You can also see that incrementals have the advantage of taking less space, but have the drawback of having dependencies.

    Hope that helps.
     
  3. dylanfan

    dylanfan Registered Member

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    Thanks :)
     
  4. TheWeaz

    TheWeaz Registered Member

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    Short version –
    A DIFF contains ALL the changes since the FULL, regardless of how many DIFF have already been done.
    An INC only contains the changes since the last INC (or the FULL if it’s the first INC).
    The FULL and all the INCs are needed to restore to the last backup date; the FULL and only the last DIFF are needed.
     
  5. Acronis Support

    Acronis Support Acronis Support Staff

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    Hello dylanfan,

    Thank you for choosing Acronis Disk Backup Software.

    We are very sorry for the delay with the response.

    In addition to what satchmo and TheWeaz said, we also recommend that you take a look at the respective FAQ article titled What is the difference between an incremental and differential image? and section 3.2 of Acronis True Image 9.0 Home User's Guide explaining the difference between incremental and differential backups in detail.

    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.
    --
    Alexey Popov
     
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