Diff Image File Size

Discussion in 'Acronis True Image Product Line' started by Roboman, May 5, 2006.

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  1. Roboman

    Roboman Registered Member

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    I'm using True Image 9.0 to do a nightly differential image back-up to an external HDD. The first file size is 35 GB. The next is around 4 GB, the next is 8GB and from then on they are 16GB.
    I have NOT run Disk Defrag and I have turned off System Restore. I'm running XP Pro SP2.

    Any thoughts?
     
  2. jmk94903

    jmk94903 Registered Member

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    Differential images grow in size since they each contain ALL the changes since the full backup. On a boot partition, there are lots of changes every day for the operating system files and Internet temp files.
     
  3. Roboman

    Roboman Registered Member

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    But 16 Gigabytes of data? That's half of all the data I have. I haven't done very much with the PC from one night to the next.

    What's the point of a differential image then?

    Also, what OS files included in the back-up change? I don't think it backs up the page file and I could clean out the browser temp files as an experiment.
     
  4. TheWeaz

    TheWeaz Registered Member

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    “What's the point of a differential image then?”
    To restore, you only need 2 files, the FULL and the DIFF. With an INC, you need the FULL, the INC and all the INCs in between.

    “Also, what OS files included in the back-up change?”
    Things not only change, they can move. If a file is moved (BootOptimizeFunction) it will be included in an INC/DIFF image.
     
  5. seekforever

    seekforever Registered Member

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    Howard Kaikow posted a link to a program he wrote that compares "disks". I haven't used it but it might help you to understand what is going on. I think, and I empasize think, that you would have to restore the original full backup to one logical drive and the original+the differential of interest to a second logical drive and then do the compare.

    Howard's post on this is:
    https://www.wilderssecurity.com/showthread.php?t=129613

    The idea behind a differential is that is faster to restore than an incremental.
     
  6. jmk94903

    jmk94903 Registered Member

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    Is the drive that you are backing up the boot drive or a drive that has only data files.

    Normally, the differential image of a data only drive/partition will be very small initially and grow slowly as data files are added or changed.

    The differential image of a boot disk/partition will grow much faster because both the data and all the Windows files change.

    Perhaps you want to make a frequent file backup of just the data folders rather than an image of the entire partition if the data is on the boot partition.
     
  7. Roboman

    Roboman Registered Member

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    It's the boot drive.
    The data isn't changing. (at least I'm not changing anything)

    I just find it hard to believe that the OS is changing/moving half of all the sectors on my drive. Why is it smaller the first time and doubles each time until it hits 1/2 the size of the full back-up (after the 3rd diff back-up)? I'm just very suspicious that something isn't right.
     
  8. TheWeaz

    TheWeaz Registered Member

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    A DIFF image contains ALL the changes since the FULL, even those that are already contained in a previous DIFF. That’s why DIFFs will always get bigger each time.
     
  9. Howard Kaikow

    Howard Kaikow Registered Member

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    Ayup, that's the reason I wrote the program.

    I've used it to compare an incremental with a full and got the expected info.

    I am a an anti-differential bigot, I will only use incrementals and have banned all differentials from my systems. The ACLU might investigate me to see if I am violating the rights of differentials.
     
  10. Howard Kaikow

    Howard Kaikow Registered Member

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    Indeed, you can even use the CompareDrives program to demonstrate how quickly lots of files change.

    Start the program and chose to compare the ACTUAL, not the one from a backup image, drive on which the OS lives with itself, the drive on which TEmporary InternetFiles lives with itself, etc.

    A few seconds aftr the program startes analysing th efirst system drive, start a few programs, such as IE.

    By the time it starts comparing the drive with itself, files should have changed.
    Ove ra day, just using mail programs, browsers and AV programs causes lots of files to change.

    On my system, I have dumb scanner software that changes a file once per minute even if the scanner is not plugged in!
     
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